PHP Cheat Sheet - 2021 Edition

Hypertext Preprocessor (PHP) is a common scripting language used for app development. PHP gets frequently updated, so it remains well-maintained and therefore attractive to those wanting a language that adapts to the developing IT world. That’s one reason we have a coding bootcamp, as languages like PHP remain popular to developers and employers. Connect with our experts to learn more about our Web Development Bootcamp.

The following PHP cheat sheet can help you review basic commands, such as before you take a PHP exam. However, since it’s a language, this guide is simply a list of the commands, and more commands can be further explained through other cheat sheets found online.

PHP Basic Commands

Including PHP in a File

<?php // place PHP code here ?>

Writing Comments

//

Indicates comments that span on one line only

#

Alternate path of producing single-line comments

/*...*/

Everything within /* and */ will not be executed, and this works across

multiple lines

 

Outputting Data

<?php echo "<h1>PHP Cheat Sheet</h1>"; ?>

 

Writing PHP Functions

function NameOfTheFunction() {

     //place PHP code here

}

VARIABLES AND CONSTANTS

Defining Variables

<?php

     $BlogPostTitle = "PHP Cheat Sheet";

?>

Data Types

Integers

Integers are non-decimal numbers within -2,147,483,648 and 2,147,483,647. They must be at least one digit and no decimal point. It can be in decimal, hexadecimal or octal.

Floats

Name for numbers with a decimal point or in exponential form.

Strings

Strings mean text. These are discussed below.

Boolean values

These are true/false statements.

Arrays

Arrays are variables that store several values. These will be discussed in detail later on.

Objects

Objects store both data as well as information on how to process the data.

Resources

Resources are references to functions and additional resources outside of PHP.

NULL

NULL means the variable doesn’t have any value.

Variable Scope

function myFunction() {

     global $a, $b;

$b = $a - $b; }

Predefined Variables

$GLOBALS

Globals accesses global variables from anywhere inside a PHP script​.

$_SERVER

Server contains information about where headers, paths and scripts are located.

$_GET

GET collects data that was sent in the URL or submitted in an HTML form.

$_POST

POST is used to collect data from an HTML form and to pass variables.

$_REQUEST

REQUEST collects data after submitting an HTML form.

Variable-handling Functions

boolval

This will retrieve the boolean value of a variable.

debug_zval_dump

This outputs a string representation of an internal zend value.

empty

Empty finds if a variable is empty or not.

floatval

This finds the float value of a variable (doubleval can also be used).

get_defined_vars

This will return 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

Finds the integer value of a variable.

is_array

Checks if a variable is an array.

is_bool

Decides whether a variable is a boolean​ of 538 is_callable

Finds out if you can call the contents of a variable as a function.

is_countable

Decides if the contents of a variable are countable.

is_float

Decides if the variable type is float. You can also use: is_double and is_real

is_int

Finds if the type of a variable is an integer, and is_integer and is_long can also work.

is_iterable

Confirm if a variable’s content is an iterable value.

is_null

Confirms if a variable’s value is NULL

is_numeric

Discovers if a variable is a number or a numeric string

is_object

Finds if a variable is an object.

is_resource

Checks whether a variable is a resource.

is_string

Confirms if the type of a variable is a string

isset

Finds if a variable has been set and is not NULL

print_r

Provides human-readable info about a variable

serialize

Makes a representation of a value that is storable

settype

Sets a variable’s type

strval

Retrieves the string value of a variable

unserialize

Produces a PHP value from a stored representation

unset

Unsets a variable

var_dump

Dumps info about a variable

var_export

Returns a string representation of a variable that can be parsed

Constants

define(name, value, true/false)

Default PHP constants:

__LINE__

Denotes the number of the current line in a file

__FILE__

FILE is the full path and filename of the file

__DIR__

The directory of the file

__FUNCTION__

The function’s name

__CLASS__

Class name, also includes 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

Indexed arrays

Arrays with a numeric index

Associative arrays

Arrays with named keys

Multidimensional arrays

Arrays that include one or more other arrays

Declaring an Array in PHP

<?php

     $cms = array("WordPress", "Joomla", "Drupal");

     echo "What is your favorite CMS? Is it " . $cms[0] . ", " .

     $cms[1] . " or " . $cms[2] . "?";

?>

Array Functions

array_change_key_case

Changes all keys in an array to lowercase or uppercase

array_chunk

Cuts an array into chunks

array_column

Finds 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

This will fill 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 the 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

Combine one or more arrays

array_merge_recursive

Combine one or more arrays recursively

array_multisort

Sorts 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

Moves an element from the beginning of an array

array_slice

Extracts a slice of an array

array_splice

Deletes 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 a 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 based on the value

asort

Sorts an associative array in ascending order according to the value

compact

Make an array containing variables and their values

count

Count all elements in an array, you can also use sizeof

current

Returns the current element in an array, you can also use poseach

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 arraykey. 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 backwards

range

Produces 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

Define Strings

Single quotes

Wrap the text in ' markers and PHP will handle it as a string.

Double quotes

Double quotes can do the same thing.

heredoc

Begin a string with <<< and an identifier. Then you can put the string in a new line. Close it by repeating the identifier.

heredoc acts like double-quoted strings.

nowdoc

heredoc is similar to single quotes. It works similarly and gets rid of the need for escape characters.

Escape Characters

\n — Line feed

\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}

\x[0-9A-Fa-f]{1,2}

\u{[0-9A-Fa-f]+}

String Functions

addcslashes()

— Character in octal notation

— Character in hexadecimal notation

— String as UTF-8 representation

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()

Changes a string of ASCII characters to hexadecimal values

chop()

Deletes 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()

Changes a string from a Cyrillic character set to

anotherconvert_uudecode()

Decodes a uuencoded

stringconvert_uuencode()

Encodes a string using

uuencodecount_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

texthebrevc()

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()

Returns 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 certain 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()

Discovers 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()

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()

Deletes 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

Arithmetic Operators

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

Assignment Operators

+= —a+=bisthesameasa=a+b -= —a-=bisthesameasa=a–b *= —a*=bisthesameasa=a*b /= —a/=bisthesameasa=a/b %= —a%=bisthesameasa=a%b

Comparison Operators

== — Equal
=== —Identical
!= — Not equal
<> — Not equal
!== —Notidentical
< — Less than
> — Greater than
<= — Less than or equal to
>= — Greater than or equal to
<=> —Lessthan,equalto,orgreaterthan

Logical Operators

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

Bitwise Operators

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

Error Control Operator

The @ sign can be used to prevent expressions from creating error messages, which is good for security reasons.

Execution Operator

PHP supports only one execution operator, which are `` (backticks). They are sometimes confused with single quotes, so be wary of this slight and common mistake. PHP tries to execute the contents of the backticks as a shell command.

Increment/Decrement Operators

++$v

Increments a variable by one, then returns it

$v++

Returns a variable, then increments it by one

--$v

Decrements the variable by one, returns it afterward

$v--

Returns the variable then decrements it by one

String Operators

.

Used to concatenate (or combine) arguments

.=

Used to append the argument on the right to the left-side argument

LOOPS IN PHP

For Loop

for (starting counter value; ending counter value; increment by which

to increase) {

// code to execute goes here

}

Foreach Loop

foreach ($InsertYourArrayName as $value) {

     // code to execute goes here

}

While Loop

while (condition that must apply) {

     // code to execute goes here

}

Do..While Loop

do {

     // code to execute goes here;

} while (condition that must apply);

CONDITIONAL STATEMENTS IN PHP

If Statement

if (condition) {

     // code to execute if condition is met

}

If..Else

if (condition) {

     // code to execute if condition is met

} else {

     // code to execute if condition is not met

}

 

If..Elseif..Else

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 x:

           code to execute if n=x;

           break;

     case y:

           code to execute if n=y;

           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;

}

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