PHP Cheat Sheet – JS Tech Road

Including PHP in a File

<?php

// place PHP code here

?>

Writing Comments

// — Denotes comments that only span one line
# — Another way of producing single-line comments
/*...*/ — Everything between /* and */ is not executed, also works across several lines

Outputting Data

In PHP, data is commonly output using echo or print. For example, the title of this blog post might be displayed on a page like this:

<?php
    echo "<h2>Hello World!</h2>";
?>

The two commands echo and print are pretty much the same. The only difference is that the former has no return value and can take several parameters, while the latter has a return value of 1 and can only take one argument.

Note: Like all other PHP commands, functions echo and print are not case sensitive. That means that when you write ECHO, EcHo, eCHO or any other variation, they will continue to work. As you will learn further on, that doesn’t apply to everything.

Writing PHP Functions

function NameOfTheFunction() {
    // PHP code here
}

Quick explanation: the first part is the function of a name (reminder: function names are not case sensitive). After that, everything between the curly braces is what the function does when called.

Defining Variables

In PHP, you denote a variable using the $ sign and assign its value using =. A typical example:

<?php
   $title = "PHP Cheat Sheet";
?>

Note:

Variables need to start with a letter or underscore (_) and can only be comprised of alpha-numeric characters
PHP variables are case sensitive, that means $myVar and $myvar are not the same thing
If your variable consists of more than one word you may write it $my_variable or $myVariable

Types of Data

Integers — Integers are non-decimal numbers between -2,147,483,648 and ,147,483,647. They must have at least one digit and no decimal point. It can be in decimal, hexadecimal, or octal.
Floats — This is the name for numbers with a decimal point or in exponential form.
Strings — This simply means text. We will talk about it in detail further below.
Boolean values — Meaning true/false statements.
Arrays — Arrays are variables that store several values. We will talk about them in detail further below.
Objects — Objects store both data and information on how to process it.
Resources — These are references to functions and resources outside of PHP.
NULL — A variable that is NULL doesn’t have any value.

There is no need to declare PHP variables in a certain way. They automatically take on the type of data they contain.

Variable Scope

Variables can be available in different scopes, meaning the part of a script you can access them. This can be global, local and static.

Any variable declared outside of a function is available globally. That means it can be accessed outside of a function as well.

If you declare a variable inside a function, it will have a local scope. The consequence is that it can only be accessed within that function.

A way around this is to prepend a local variable with global. That way, it becomes part of the global scope:

function myFunction() {
    global $a, $b;
    $b = $a - $b;
}

In both cases, the variable becomes part of the $GLOBALS variable mentioned below.

Finally, it’s also possible to add static in front of a local variable. That way, it won’t be deleted after its function is executed and can be reused.

Predefined Variables

Reserve PHP variables, accessible from anywhere, regardless of scope.

$GLOBALS — Used to access global variables from anywhere inside a PHP script
$_SERVER — Contains information about the locations of headers, paths, and scripts
$_GET — Can collect data that was sent in the URL or submitted in an HTML form
$_POST — Used to gather data from an HTML form and to pass variables
$_REQUEST — Also collects data after submitting an HTML form

Variable-Handling Functions

There are a whole bunch of functions to work with variables:

boolval — Used to retrieve the boolean value of a variable
debug_zval_dump — Outputs a string representation of an internal zend value
empty — Checks whether a variable is empty or not
floatval — Get the float value of a variable (doubleval is another possibility)
get_defined_vars — Returns an array of all defined variables
get_resource_type — Returns the resource type
gettype — Retrieves the variable type
import_request_variables — Import GET/POST/Cookie variables into the global scope
intval — Find the integer value of a variable
is_array — Checks whether a variable is an array
is_bool — Finds out if a variable is a boolean
is_callable — Verify whether you can call the contents of a variable as a function
is_countable — Check whether the contents of a variable are countable
is_float — Find out if the type of a variable is float, alternatives: is_double and is_real
is_int — Check if the type of a variable is an integer, is_integer and is_long also works
is_iterable — Verify that a variable’s content is an iterable value
is_null — Checks whether a variable’s value is NULL
is_numeric — Find out if a variable is a number or a numeric string
is_object — Determines whether a variable is an object
is_resource — Check if a variable is a resource
is_scalar — Tests if a variable is a scalar
is_string — Find out whether the type of a variable is a string
isset — Determine if a variable has been set and is not NULL
print_r — Provides human-readable information about a variable
serialize — Generates a representation of a value that is storable
settype — Sets a variable’s type
strval — Retrieves the string value of a variable
unserialize — Creates a PHP value from a stored representation
unset — Unsets a variable
var_dump — Dumps information about a variable
var_export — Outputs or returns a string representation of a variable that can be parsed

Constants

Aside from variables, you can also define constants which also store values. In contrast to variables their value can not be changed, it’s locked in.

In PHP you can define a constant:

define(name, value, true/false)

The first is the name, the second the constant’s value and the third parameter whether its name should be case sensitive (the default is false).

Constants are useful since they allow you to change the value for an entire script in one place instead of having to replace every instance of it. They are also global in nature, meaning they can be accessed from anywhere.

Aside from user-defined constants, there also a number of default PHP constants:

__LINE__ — Denotes the number of the current line in a file
__FILE__ — Is the full path and filename of the file
__DIR__ — The directory of the file
__FUNCTION__ — Name of the function
__CLASS__ — Class name, includes the namespace it was declared in
__TRAIT__ — The trait name, also includes the namespace
__METHOD__ — The class method name
__NAMESPACE__ — Name of the current namespace

PHP Arrays – Grouped Values

Arrays are a way to organize several values in a single variable so that they can be used together. While functions are for blocks of code, arrays are for the values – a placeholder for larger chunks of information.

In PHP there are different types of arrays:

Indexed arrays – Arrays that have a numeric index
Associative arrays – Arrays where the keys are named
Multidimensional arrays – Arrays that contain one or more other arrays

Declaring an Array in PHP

Arrays in PHP are created with the array()

<?php
  $cms = array("Banna", "Apple", "Pear");
  echo "What is your favorite fruit? Is it " . $cms[0] . ", " . $cms[1] . " or " . $cms[2] . "?";
?>

Array keys can either be strings or integers.

How to create an array with key value pairs in PHP?

PHP offers us a special type of array called an Associative Array that allows us to create an array with Key-Value pairs. The syntax for creating an Associative Array is as follows:

Syntax 1: Using array() constructor

$arrayVariable = array(
    key1 => value1,
    key2 => value2,
    key3 => value3,
    ...
    keyN => valueN,
);

Syntax 2: Using shorthand notation

$arrayVariable = [
    key1 => value1,
    key2 => value2,
    key3 => value3,
    ...
    keyN => valueN,
];

Array Functions

array_change_key_case — Changes all keys in an array to uppercase or lowercase
array_chunk — Splits an array into chunks
array_column — Retrieves the values from a single column in an array
array_combine — Merges the keys from one array and the values from another into a new array
array_count_values — Counts all values in an array
array_diff — Compares arrays, returns the difference (values only)
array_diff_assoc — Compares arrays, returns the difference (values and keys)
array_diff_key — Compares arrays, returns the difference (keys only)
array_diff_uassoc — Compares arrays (keys and values) through a user callback function
array_diff_ukey — Compares arrays (keys only) through a user callback function
array_fill — Fills an array with values
array_fill_keys — Fills an array with values, specifying keys
array_filter — Filters the elements of an array via a callback function
array_flip — Exchanges all keys in an array with their associated values
array_intersect — Compare arrays and return their matches (values only)
array_intersect_assoc — Compare arrays and return their matches (keys and values)
array_intersect_key — Compare arrays and return their matches (keys only)
array_intersect_uassoc — Compare arrays via a user-defined callback function (keys and values)
array_intersect_ukey — Compare arrays via a user-defined callback function (keys only)
array_key_exists — Checks if a specified key exists in an array, alternative: key_exists
array_keys — Returns all keys or a subset of keys in an array
array_map — Applies a callback to the elements of a given array
array_merge — Merge one or several arrays
array_merge_recursive — Merge one or more arrays recursively
array_multisort — Sorts of multiple or multi-dimensional arrays
array_pad — Inserts a specified number of items (with a specified value) into an array
array_pop — Deletes an element from the end of an array
array_product — Calculate the product of all values in an array
array_push — Push one or several elements to the end of the array
array_rand — Pick one or more random entries out of an array
array_reduce — Reduce the array to a single string using a user-defined function
array_replace — Replaces elements in the first array with values from following arrays
array_replace_recursive — Recursively replaces elements from later arrays into the first array
array_reverse — Returns an array in reverse order
array_search — Searches the array for a given value and returns the first key if successful
array_shift — Shifts an element from the beginning of an array
array_slice — Extracts a slice of an array
array_splice — Removes a portion of the array and replaces it
array_sum — Calculate the sum of the values in an array
array_udiff — Compare arrays and return the difference using a user function (values only)
array_udiff_assoc — Compare arrays and return the difference using default and a user function (keys and values)
array_udiff_uassoc — Compare arrays and return the difference using two user functions (values and keys)
array_uintersect — Compare arrays and return the matches via user function (values only)
array_uintersect_assoc — Compare arrays and return the matches via a default user function (keys and values)
array_uintersect_uassoc — Compare arrays and return the matches via two user functions (keys and values)
array_unique — Removes duplicate values from an array
array_unshift — Adds one or more elements to the beginning of an array
array_values — Returns all values of an array
array_walk — Applies a user function to every element in an array
array_walk_recursive — Recursively applies a user function to every element of an array
arsort — Sorts an associative array in descending order according to the value
asort — Sorts an associative array in ascending order according to the value
compact — Create an array containing variables and their values
count — Count all elements in an array, alternatively use sizeof
current — Returns the current element in an array, an alternative is pos
each — Return the current key and value pair from an array
end — Set the internal pointer to the last element of an array
extract — Import variables from an array into the current symbol table
in_array — Checks if a value exists in an array
key — Fetches a key from an array
krsort — Sorts an associative array by key in reverse order
ksort — Sorts an associative array by key
list — Assigns variables as if they were an array
natcasesort — Sorts an array using a “natural order” algorithm independent of case
natsort — Sorts an array using a “natural order” algorithm
next — Advance the internal pointer of an array
prev — Move the internal array pointer backward
range — Creates an array from a range of elements
reset — Set the internal array pointer to its first element
rsort — Sort an array in reverse order
shuffle — Shuffle an array
sort — Sorts an indexed array in ascending order
uasort — Sorts an array with a user-defined comparison function
uksort — Arrange an array by keys using a user-defined comparison function
usort — Categorize an array by values using a comparison function defined by the user

PHP Strings

In programming, speech strings are nothing more than text. As we have settled earlier, they are also a valid value for variables.

Defining Strings

In PHP there are several ways to define strings:

Single quotes — This is the simplest way. Just wrap your text in ' markers and PHP will handle it as a string.
Double quotes — As an alternative you can use ". When you do, it’s possible to use the escape characters below to display special characters.
heredoc — Begin a string with <<< and an identifier, then put the string in a new line. Close it in another line by repeating the identifier. heredoc behaves like double-quoted strings.
nowdoc — Is what heredoc is for double-quoted strings but for single quotes. It works the same way and eliminates the need for escape characters.

Note: Strings can contain variables, arrays, and objects.

Escape Characters

\n — Linefeed
\r — Carriage return
\t — Horizontal tab
\v — Vertical tab
\e — Escape
\f — Form feed
\\ — Backslash
\$ — Dollar sign
/' — Single quote
\" — Double quote
\[0-7]{1,3} — Character in octal notation
\x[0-9A-Fa-f]{1,2} — Character in hexadecimal notation
\u{[0-9A-Fa-f]+} — String as UTF-8 representation

String Functions

addcslashes() — Returns a string with backslashes in front of specified characters
addslashes() — Returns a string with backslashes in front of characters that need to be escaped
bin2hex() — Converts a string of ASCII characters to hexadecimal values
chop() — Removes space or other characters from the right end of a string
chr() — Returns a character from a specified ASCII value
chunk_split() — Splits a string into a series of smaller chunks
convert_cyr_string() — Converts a string from a Cyrillic character set to another
convert_uudecode() — Decodes a uuencoded string
convert_uuencode() — Encodes a string using uuencode
count_chars() — Returns information about the characters in a string
crc32() — Calculates a 32-bit CRC for a string
crypt() — Returns a hashed string
echo() or echo '' — Outputs one or several strings
explode() — Breaks down a string into an array
fprintf() — Writes a formatted string to a specified output stream
get_html_translation_table() — Returns the translation table used by htmlspecialchars() and htmlentities()
hebrev() — Transforms Hebrew text to visual text
hebrevc() — Converts Hebrew text to visual text and implements HTML line breaks
hex2bin() — Translate hexadecimal values to ASCII characters
html_entity_decode() — Turns HTML entities to characters
htmlentities() — Converts characters to HTML entities
htmlspecialchars_decode() — Transforms special HTML entities to characters
htmlspecialchars() — Switches predefined characters to HTML entities
implode() — Retrieves a string from the elements of an array, same as join()
lcfirst() — Changes a string’s first character to lowercase
levenshtein() — Calculates the Levenshtein distance between two strings
localeconv() — Returns information about numeric and monetary formatting for the locale
ltrim() — Removes spaces or other characters from the left side of a string
md5() — Calculates the MD5 hash of a string and returns it
md5_file() — Calculates the MD5 hash of a file
metaphone() — Provides the metaphone key of a string
money_format() — Returns a string as a currency string
nl_langinfo() — Gives specific locale information
nl2br() — Inserts HTML line breaks for each new line in a string
number_format() — Formats a number including grouped thousands
ord() — Returns the ASCII value of a string’s first character
parse_str() — Parses a string into variables
print() — Outputs one or several strings
printf() — Outputs a formatted string
quoted_printable_decode() — Converts a quoted-printable string to 8-bit binary
quoted_printable_encode() — Goes from 8-bit string to a quoted-printable string
quotemeta() — Returns a string with a backslash before metacharacters
rtrim() — Strips whitespace or other characters from the right side of a string
setlocale() — Sets locale information
sha1() — Calculates a string’s SHA-1 hash
sha1_file() — Does the same for a file
similar_text() — Determines the similarity between two strings
soundex() — Calculates the soundex key of a string
sprintf() — Returns a formatted string
sscanf() — Parses input from a string according to a specified format
str_getcsv() — Parses a CSV string into an array
str_ireplace() — Replaces specified characters in a string with specified replacements (case-insensitive)
str_pad() — Pads a string to a specified length
str_repeat() — Repeats a string a preset number of times
str_replace() — Replaces specified characters in a string (case-sensitive)
str_rot13() — Performs ROT13 encoding on a string
str_shuffle() — Randomly shuffles the characters in a string
str_split() — Splits strings into arrays
str_word_count() — Returns the number of words in a string
strcasecmp() — Case-insensitive comparison of two strings
strcmp() — Binary safe string comparison (case sensitive)
strcoll() — Compares two strings based on locale
strcspn() — Returns the number of characters found in a string before the occurrence of specified characters
strip_tags() — Removes HTML and PHP tags from a string
stripcslashes() — Opposite of addcslashes()
stripslashes() — Opposite of addslashes()
stripos() — Finds the position of the first occurrence of a substring within a string (case insensitive)
stristr() — Case-insensitive version of strstr()
strlen() — Returns the length of a string
strnatcasecmp() — Case-insensitive comparison of two strings using a “natural order” algorithm
strnatcmp() — Same as the aforementioned but case sensitive
strncasecmp() — String comparison of a defined number of characters (case insensitive)
strncmp() — Same as above but case-sensitive
strpbrk() — Searches a string for any number of characters
strpos() — Returns the position of the first occurrence of a substring in a string (case sensitive)
strrchr() — Finds the last occurrence of a string within another string
strrev() — Reverses a string
strripos() — Finds the position of the last occurrence of a string’s substring (case insensitive)
strrpos() — Same as strripos() but case sensitive
strspn() — The number of characters in a string with only characters from a specified list
strstr() — Case-sensitive search for the first occurrence of a string inside another string
strtok() — Splits a string into smaller chunks
strtolower() — Converts all characters in a string to lowercase
strtoupper() — Same but for uppercase letters
strtr() — Translates certain characters in a string, alternative: strchr()
substr() — Returns a specified part of a string
substr_compare() — Compares two strings from a specified start position up to a certain length, optionally case sensitive
substr_count() — Counts the number of times a substring occurs within a string
substr_replace() — Replaces a substring with something else
trim() — Removes space or other characters from both sides of a string
ucfirst() — Transforms the first character of a string to uppercase
ucwords() — Converts the first character of every word in a string to uppercase
vfprintf() — Writes a formatted string to a specified output stream
vprintf() — Outputs a formatted string
vsprintf() — Writes a formatted string to a variable
wordwrap() — Shortens a string to a given number of characters

PHP Operators

Operators allow you to perform operations with values, arrays, and variables. There are several different types.

Arithmetic Operators

Your standard mathematic operators.

+ — Addition
- — Subtraction
* — Multiplication
/ — Division
% — Modulo (the remainder of value divided by another)
** — Exponentiation

Assignment Operators

Besides the standard assignment operator (=), you also have the following options:

+= — a += b is the same as a = a + b
-= — a -= b is the same as a = a – b
*= — a *= b is the same as a = a * b
/= — a /= b is the same as a = a / b
%= — a %= b is the same as a = a % b

Comparison Operators

== — Equal
=== — Identical
!= — Not equal
<> — Not equal
!== — Not identical
< — Less than
> — Greater than
<= — Less than or equal to
>= — Greater than or equal to
<=> — Less than, equal to, or greater than

Logical Operators

and — And
or — Or
xor — Exclusive or
! — Not
&& — And
|| — Or

Bitwise Operators

& — And
| — Or (inclusive or)
^ — Xor (exclusive or)
~ — Not
<< — Shift left
>> — Shift right

Error Control Operator

You can use the @ sign to prevent expressions from generating error messages. This is often important for security reasons, for example, to keep confidential information safe.

Execution Operator

PHP supports one execution operator, which is `` (backticks). These are not single-quotes! PHP will attempt to execute the contents of the backticks as a shell command.

Increment/Decrement Operators

++$i — Increments a variable by one, then returns it
$i++ — Returns a variable, then increments it by one
--$i — Decrements the variable by one, returns it afterward
$i-- — Returns the variable then decrements it by one

String Operators

. — Used to concatenate (mean combine) arguments
.= — Used to append the argument on the right to the left-side argument

Loops in PHP

Loops are very common in programming. They allow you to run through the same block of code under different circumstances. PHP has several different ones.

For Loop

This type goes through a block of code a specified number of times:

for ($i = 0; $i <= 10; $i++) {
    // code to execute goes here
}

Foreach Loop

A loop using foreach runs through each element in an array:

foreach ($InsertYourArrayName as $value) {
    // code to execute goes here
}
// or
foreach ($array as $key => $value)

While Loop

Loops through a block of code as long as a specified condition is true.

while (condition that must apply) {
    // code to execute goes here
}

Do…While Loop

The final PHP loop runs a code snippet once, then repeats the loop as long as the given condition is true.

do {
    // code to execute goes here;
} while (condition that must apply);

Conditional Statements

If/else statements are similar to loops. They are statements for running code only under certain circumstances. You have several options:

If/elseif/else Statement

if (condition) {
    // code to execute if condition is met
} elseif (condition) {
    // code to execute if this condition is met
} else {
    // code to execute if none of the conditions are met
}

Switch Statement

switch (n) {
    case 1:
        code to execute if n=1;
        break;
    case 'abc':
        code to execute if n='abc';
        break;
    case z:
        code to execute if n=z;
        break;
    // add more cases as needed
    default:
        code to execute if n is neither of the above;
}

Working with Forms in PHP

$_GET and $_POST help to collect data sent via a form.

Using GET vs POST

GET collects data via URL parameters. That means all variable names and their values are contained in the page address.

The advantage of this is that you’re able to bookmark the information. Keep in mind that it also means that the information is visible to everyone. For that reason, GET is not suitable for sensitive information such as passwords. It also limits the amount of data that can be sent in ca 2000 characters.

POST, on the other hand, uses the HTTP POST method to pass on variables. This makes the data invisible to third parties, as it is sent in the HTTP body. You are not able to bookmark it.

With POST, there are no limits to the amount of information you can send. Aside from that, it also has advanced functionality and is therefore preferred by developers.

Form Security

The most important issue when it comes to web forms is security. If not set up properly, they are vulnerable to cross-scripting attacks. The hackers add scripts to unsecured web forms to use them for their own purpose.

PHP offers following function to thwart those attacks:

htmlspecialchars()
trim()
stripslashes()

Required Fields, Error Messages and Data Validation

PHP is able to define required fields (you can’t submit the form without filling them out), display error messages if some information is missing and to validate data. We have already talked about the necessary tools to do so.

For example, you can simply define variables for your form fields and use the empty() function to check if they have values. After that, create a simple if/else statement to either send the submitted data or output an error message.

The next step is to check the submitted data for validity. For that, PHP offers a number of filters such as FILTER_VALIDATE_EMAIL to make sure a submitted email address has the right format.

Regular Exprressions (RegEx)

Syntax

$exp = "/w3schools/i";

RegEx Functions

preg_match()

Returns 1 if the pattern was found in the string and 0 if not

preg_match_all()

Returns the number of times the pattern was found in the string, which may also be 0

preg_replace()

Returns a new string where matched patterns have been replaced with another string

RegEx Modifiers

i Performs a case-insensitive search

m Performs a multiline search (patterns that search for the beginning or end of a string will match the beginning or end of each line)

u Enables correct matching of UTF-8 encoded patterns

RegEx Patterns

[abc] – Find one character from the options between the brackets

[^abc] – Find any character NOT between the brackets

[0-9] – Find one character from the range 0 to 9

Metacharacters

| Find a match for any one of the patterns separated by | as in: cat|dog|fish

. Find just one instance of any character

^ Finds a match as the beginning of a string as in: ^Hello

$ Finds a match at the end of the string as in: World$

\d Find a digit

\s Find a whitespace character

\b Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b

\uxxxx Find the Unicode character specified by the hexadecimal number xxxx

Quantifiers

n+ Matches any string that contains at least one n

n* Matches any string that contains zero or more occurrences of n

n? Matches any string that contains zero or one occurrences of n

n{x} Matches any string that contains a sequence of X n’s

n{x,y} Matches any string that contains a sequence of X to Y n’s

n{x,} Matches any string that contains a sequence of at least X n’s

Grouping

Use parentheses ( ) to apply quantifiers to entire patterns. They cal also be used to select parts of the pattern to be used as a match.

<?php
  $str = "Apples and bananas.";
  $pattern = "/ba(na){2}/i";
  echo preg_match($pattern, $str); // Outputs 1
?>

PHP Functions

A function is a block of statements that can be used repeatedly in a program.
A function will not execute automatically when a page loads.
A function will be executed by a call to the function.

Default Argument Value

<?php declare(strict_types=1); // strict requirement
function setHeight(int $minheight = 100) {
  echo "The height is : $minheight <br>";
}
setHeight(50);
setHeight(); // will use the default value of 100

?>

PHP Filters

Filters are used to validate and filter data that is coming from insecure sources. As mentioned, a common example is user input. PHP offers a number of filter functions and constants for that:

Filter Functions

filter_has_var() — Checks if a variable of the specified type exists
filter_id() — Returns the ID belonging to a named filter
filter_input() — Retrieves a specified external variable by name and optionally filters it
filter_input_array() — Pulls external variables and optionally filters them
filter_list() — Returns a list of all supported filters
filter_var_array() — Gets multiple variables and optionally filters them
filter_var() — Filters a variable with a specified filter

Filter Constants

FILTER_VALIDATE_BOOLEAN — Validates a boolean
FILTER_VALIDATE_EMAIL — Certifies an e-mail address
FILTER_VALIDATE_FLOAT — Confirms a float
FILTER_VALIDATE_INT — Verifies an integer
FILTER_VALIDATE_IP — Validates an IP address
FILTER_VALIDATE_REGEXP — Confirms a regular expression
FILTER_VALIDATE_URL — Validates a URL
FILTER_SANITIZE_EMAIL — Removes all illegal characters from an e-mail address
FILTER_SANITIZE_ENCODED — Removes/Encodes special characters
FILTER_SANITIZE_MAGIC_QUOTES — Applies addslashes()
FILTER_SANITIZE_NUMBER_FLOAT — Removes all characters, except digits, +- and .,eE
FILTER_SANITIZE_NUMBER_INT — Gets rid of all characters except digits and + –
FILTER_SANITIZE_SPECIAL_CHARS — Removes special characters
FILTER_SANITIZE_FULL_SPECIAL_CHARS — Converts special characters to HTML entities
FILTER_SANITIZE_STRING — Removes tags/special characters from a string, alternative: FILTER_SANITIZE_STRIPPED
FILTER_SANITIZE_URL — Rids all illegal characters from a URL
FILTER_UNSAFE_RAW —Do nothing, optionally strip/encode special characters
FILTER_CALLBACK — Call a user-defined function to filter data

HTTP Functions in PHP

PHP also has the functionality to manipulate data sent to the browser from the webserver.

HTTP Functions

header() — Sends a raw HTTP header to the browser
headers_list() — A list of response headers ready to send (or already sent)
headers_sent() — Checks if and where the HTTP headers have been sent
setcookie() — Defines a cookie to be sent along with the rest of the HTTP headers
setrawcookie() — Defines a cookie (without URL encoding) to be sent along

Working with MySQL

Many platforms that are based on PHP work with a MySQL database in the background.

MySQL Functions

mysqli_affected_rows() — The number of affected rows in the previous MySQL operation
mysqli_autocommit() — Turn auto-committing database modifications on or off
mysqli_change_user() — Changes the user of the specified database connection
mysqli_character_set_name() — The default character set for the database connection
mysqli_close() — Closes an open database connection
mysqli_commit() — Commits the current transaction
mysqli_connect_errno() — The error code from the last connection error
mysqli_connect_error() — The error description from the last connection error
mysqli_connect() — Opens a new connection to the MySQL server
mysqli_data_seek() — Moves the result pointer to an arbitrary row in the result set
mysqli_debug() — Performs debugging operations
mysqli_dump_debug_info() — Dumps debugging information into a log
mysqli_errno() — The last error code for the most recent function call
mysqli_error_list() — A list of errors for the most recent function call
mysqli_error() — The last error description for the most recent function call
mysqli_fetch_all() — Fetches all result rows as an array
mysqli_fetch_array() — Fetches a result row as an associative, a numeric array, or both
mysqli_fetch_assoc() — Fetches a result row as an associative array
mysqli_fetch_field_direct() — Metadata for a single field as an object
mysqli_fetch_field() — The next field in the result set as an object
mysqli_fetch_fields() — An array of objects that represent the fields in a result set
mysqli_fetch_lengths() — The lengths of the columns of the current row in the result set
mysqli_fetch_object() — The current row of a result set as an object
mysqli_fetch_row() — Fetches one row from a result set and returns it as an enumerated array
mysqli_field_count() — The number of columns for the most recent query
mysqli_field_seek() — Sets the field cursor to the given field offset
mysqli_field_tell() — The position of the field cursor
mysqli_free_result() — Frees the memory associated with a result
mysqli_get_charset() — A character set object
mysqli_get_client_info() — The MySQL client library version
mysqli_get_client_stats() — Returns client per-process statistics
mysqli_get_client_version() — The MySQL client library version as an integer
mysqli_get_connection_stats() — Statistics about the client connection
mysqli_get_host_info() — The MySQL server hostname and the connection type
mysqli_get_proto_info() — The MySQL protocol version
mysqli_get_server_info() — Returns the MySQL server version
mysqli_get_server_version() — The MySQL server version as an integer
mysqli_info() — Returns information about the most recently executed query
mysqli_init() — Initializes MySQLi and returns a resource for use with mysqli_real_connect()
mysqli_insert_id() — Returns the auto-generated ID used in the last query
mysqli_kill() — Asks the server to kill a MySQL thread
mysqli_more_results() — Checks if there are more results from a multi-query
mysqli_multi_query() — Performs one or more queries on the database
mysqli_next_result() — Prepares the next result set from mysqli_multi_query()
mysqli_num_fields() — The number of fields in a result set
mysqli_num_rows() — The number of rows in a result set
mysqli_options() — Sets extra connect options and affect behavior for a connection
mysqli_ping() — Pings a server connection or tries to reconnect if it has gone down
mysqli_prepare() — Prepares an SQL statement for execution
mysqli_query() — Performs a query against the database
mysqli_real_connect() — Opens a new connection to the MySQL server
mysqli_real_escape_string() — Escapes special characters in a string for use in an SQL statement
mysqli_real_query() — Executes an SQL query
mysqli_reap_async_query() — Returns the result from async query
mysqli_refresh() — Refreshes tables or caches or resets the replication server information
mysqli_rollback() — Rolls back the current transaction for the database
mysqli_select_db() — Changes the default database for the connection
mysqli_set_charset() — Sets the default client character set
mysqli_set_local_infile_default() — Unsets a user-defined handler for the LOAD LOCAL INFILE command
mysqli_set_local_infile_handler() — Sets a callback function for the LOAD DATA LOCAL INFILE command
mysqli_sqlstate() — Returns the SQLSTATE error code for the last MySQL operation
mysqli_ssl_set() — Establishes secure connections using SSL
mysqli_stat() — The current system status
mysqli_stmt_init() — Initializes a statement and returns an object for use with mysqli_stmt_prepare()
mysqli_store_result() — Transfers a result set from the last query
mysqli_thread_id() — The thread ID for the current connection
mysqli_thread_safe() — Returns if the client library is compiled as thread-safe
mysqli_use_result() — Initiates the retrieval of a result set from the last query executed using the mysqli_real_query()
mysqli_warning_count() — The number of warnings from the last query in the connection

Date/Time Functions

checkdate() — Checks the validity of a Gregorian date
date_add() — Adds a number of days, months, years, hours, minutes and seconds to a date object
date_create_from_format() — Returns a formatted DateTime object
date_create() — Creates a new DateTime object
date_date_set() — Sets a new date
date_default_timezone_get() — Returns the default timezone used by all functions
date_default_timezone_set() — Sets the default timezone
date_diff() — Calculates the difference between two dates
date_format() — Returns a date formatted according to a specific format
date_get_last_errors() — Returns warnings or errors found in a date string
date_interval_create_from_date_string() — Sets up a DateInterval from relative parts of a string
date_interval_format() — Formats an interval
date_isodate_set() — Sets a date according to ISO 8601 standards
date_modify() — Modifies the timestamp
date_offset_get() — Returns the offset of the timezone
date_parse_from_format() — Returns an array with detailed information about a specified date, according to a specified format
date_parse() — Returns an array with detailed information about a specified date
date_sub() — Subtracts days, months, years, hours, minutes and seconds from a date
date_sun_info() — Returns an array containing information about sunset/sunrise and twilight begin/end for a specified day and location
date_sunrise() — The sunrise time for a specified day and location
date_sunset() — The sunset time for a specified day and location
date_time_set() — Sets the time
date_timestamp_get() — Returns the Unix timestamp
date_timestamp_set() — Sets the date and time based on a Unix timestamp
date_timezone_get() — Returns the time zone of a given DateTime object
date_timezone_set() — Sets the time zone for a DateTime object
date() — Formats a local date and time
getdate() — Date/time information of a timestamp or the current local date/time
gettimeofday() — The current time
gmdate() — Formats a GMT/UTC date and time
gmmktime() — The Unix timestamp for a GMT date
gmstrftime() — Formats a GMT/UTC date and time according to locale settings
idate() — Formats a local time/date as an integer
localtime() — The local time
microtime() — The current Unix timestamp with microseconds
mktime() — The Unix timestamp for a date
strftime() — Formats a local time and/or date according to locale settings
strptime() — Parses a time/date generated with strftime()
strtotime() — Transforms an English textual DateTime into a Unix timestamp
time() — The current time as a Unix timestamp
timezone_abbreviations_list() — Returns an array containing dst, offset, and the timezone name
timezone_identifiers_list() — An indexed array with all timezone identifiers
timezone_location_get() — Location information for a specified timezone
timezone_name_from_abbr() — Returns the timezone name from an abbreviation
timezone_name_get() — The name of the timezone
timezone_offset_get() — The timezone offset from GMT
timezone_open() — Creates a new DateTimeZone object
timezone_transitions_get() — Returns all transitions for the timezone
timezone_version_get() — Returns the version of the timezonedb

Date and Time Formatting

d — 01 to 31
j — 1 to 31
D — Mon through Sun
l — Sunday through Saturday
N — 1 (for Mon) through 7 (for Sat)
w — 0 (for Sun) through 6 (for Sat)
m — Months, 01 through 12
n — Months, 1 through 12
F — January through December
M — Jan through Dec
Y — Four digits year (e.g. 2018)
y — Two digits year (e.g. 18)
L — Defines whether it’s a leap year (1 or 0)
a — am and pm
A — AM and PM
g — Hours 1 through 12
h — Hours 01 through 12
G — Hours 0 through 23
H — Hours 00 through 23
i — Minutes 00 to 59
s — Seconds 00 to 59

PHP Errors

Error Functions

debug_backtrace() — Used to generate a backtrace
debug_print_backtrace() — Prints a backtrace
error_get_last() — Gets the last error that occurred
error_log() — Sends an error message to the web server’s log, a file or a mail account
error_reporting() — Specifies which PHP errors are reported
restore_error_handler() — Reverts to the previous error handler function
restore_exception_handler() — Goes back to the previous exception handler
set_error_handler() — Sets a user-defined function to handle script errors
set_exception_handler() — Sets an exception handler function defined by the user
trigger_error() — Generates a user-level error message, you can also use user_error()

Error Constants

E_ERROR — Fatal run-time errors that cause the halting of the script and can’t be recovered from
E_WARNING — Non-fatal run-time errors, execution of the script continues
E_PARSE — Compile-time parse errors, should only be generated by the parser
E_NOTICE — Run-time notices that indicate a possible error
E_CORE_ERROR — Fatal errors at PHP initialization, like an E_ERROR in PHP core
E_CORE_WARNING — Non-fatal errors at PHP startup, similar to E_WARNING but in PHP core
E_COMPILE_ERROR — Fatal compile-time errors generated by the Zend Scripting Engine
E_COMPILE_WARNING — Non-fatal compile-time errors by the Zend Scripting Engine
E_USER_ERROR — Fatal user-generated error, set by the programmer using trigger_error()
E_USER_WARNING — Non-fatal user-generated warning
E_USER_NOTICE — User-generated notice by trigger_error()
E_STRICT — Suggestions by PHP to improve your code (needs to be enabled)
E_RECOVERABLE_ERROR — Catchable fatal error caught by a user-defined handle
E_DEPRECATED — Enable this to receive warnings about a code which is not future-proof
E_USER_DEPRECATED — User-generated warning for deprecated code
E_ALL — All errors and warnings except E_STRICT