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Catalog / PHP Cheatsheet

PHP Cheatsheet

A comprehensive cheat sheet covering essential PHP syntax, functions, and best practices for web development.

Core Syntax & Data Types

Basic Syntax

Opening tag

<?php

Closing tag

?>

Statement terminator

;

Comments (single-line)

// or #

Comments (multi-line)

/* ... */

Echoing output

echo 'Hello, world!'; or print 'Hello, world!';

Data Types

Scalar Types:

  • int: Integer
  • float: Floating-point number
  • string: Sequence of characters
  • bool: Boolean (true or false)

Compound Types:

  • array: Ordered map
  • object: Instance of a class
  • callable: can be used as parameter for functions such as call_user_func()

Special Types:

  • resource: A reference to an external resource
  • null: Represents a variable with no value

Variable Declaration

Declaration

$variable_name = value;

Example

 
$name = "John Doe";
$age = 30;

Operators & Control Structures

Operators

Arithmetic

+, -, *, /, %

Assignment

=, +=, -=, *=, /=, %=

Comparison

==, ===, !=, !==, >, <, >=, <=

Increment/Decrement

++, --

Logical

&& (and), || (or), ! (not)

String

. (concatenation), .= (concatenation assignment)

Control Structures

Conditional Statements:

if (condition) {
  // code to be executed if condition is true
} elseif (condition) {
  // code to be executed if first condition is false and this condition is true
} else {
  // code to be executed if all conditions are false
}

Switch Statement:

switch (expression) {
  case value1:
    // code to be executed if expression = value1
    break;
  case value2:
    // code to be executed if expression = value2
    break;
  default:
    // code to be executed if expression is different from both value1 and value2
}

Loops:

for ($i = 0; $i < 10; $i++) {
  // code to be executed
}

while (condition) {
  // code to be executed
}

do {
  // code to be executed
} while (condition);

foreach ($array as $value) {
  // code to be executed
}

Functions & Arrays

Functions

Definition

 
function functionName($arg1, $arg2) {
  // code to be executed
  return $returnValue;
}

Calling a function

functionName(value1, value2);

Example with default argument

 
function greet($name = "Guest") {
  echo "Hello, $name!";
}

Arrays

Indexed Arrays:

$colors = array("Red", "Green", "Blue");
echo $colors[0]; // Output: Red

Associative Arrays:

$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";

Multidimensional Arrays:

$cars = array(
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
);

echo $cars[0][0].": In stock: ".$cars[0][1].", sold: ".$cars[0][2].".";

Array Functions

count()

Returns the number of elements in an array.

array_push()

Adds one or more elements to the end of an array.

array_pop()

Removes the last element from an array.

array_shift()

Removes the first element from an array.

array_unshift()

Adds one or more elements to the beginning of an array.

array_merge()

Merges one or more arrays into one array.

in_array()

Checks if a value exists in an array.

Classes & Objects

Class Definition 

class ClassName {
  // Properties
  public $property1;
  private $property2;
  protected $property3;

  // Methods
  public function method1() {
    // Code
  }

  private function method2() {
    // Code
  }

  protected function method3() {
    // Code
  }
}

Visibility:

  • public: Accessible from anywhere.
  • private: Accessible only within the class.
  • protected: Accessible within the class and by inheriting classes.

Object Instantiation

Creating an object

 
$object = new ClassName();

Accessing properties and methods

 
$object->property1 = "Value";
echo $object->method1();

Constructors & Destructors

Constructor:

class MyClass {
  public function __construct() {
    // Code to be executed when an object is created
  }
}

Destructor:

class MyClass {
  public function __destruct() {
    // Code to be executed when an object is destroyed
  }
}

Inheritance

Extending a class

 
class ChildClass extends ParentClass {
  // Code
}

Overriding methods

A child class can override methods of the parent class.
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