PHP Coding Cheat Sheet

PHP Coding Cheat Sheet

PHP is one of the most popular server-side scripting languages for building dynamic and interactive web applications. Its simplicity and flexibility have made it a favourite among both beginners and seasoned developers. This cheat sheet provides a quick reference to essential PHP concepts—from basic syntax and variable handling to advanced topics like object-oriented programming and error management—allowing you to code more efficiently and debug faster. Whether you’re just starting out or looking to polish your skills, this guide offers clear, concise examples and practical tips to help you master PHP.

Designed as a comprehensive, printable resource, this PHP Coding Cheat Sheet is an indispensable tool for web developers. It covers a wide range of topics, including loops, conditional statements, arrays, functions, file inclusion, and database interactions with PDO. With detailed explanations and real-world examples, the cheat sheet simplifies complex concepts and ensures that you have a reliable reference at your fingertips. Download, print, and keep this guide nearby as you build, maintain, and improve your web projects.

ConceptSyntax/ExampleNotes
PHP Opening & Closing Tags <?php
// Your PHP code here
?> 		Indicates the start and end of a PHP script
Echo Statementecho "Hello, World!";Outputs text to the browser
Variables$variable = value;Variables start with a $; no type declaration needed
Comments// single-line
/* multi-line */		Adds notes to code
If Statementif (condition) { ... }Conditional logic
For Loopfor ($i = 0; $i < 10; $i++) { ... }Iterates a fixed number of times
While Loopwhile (condition) { ... }Repeats while condition is true
Do-While Loopdo { ... } while (condition);Executes at least once
Foreach Loopforeach ($array as $value) { ... }Iterates over arrays
Switch Statementswitch($var) { case 'a': ... break; default: ... }Multi-branch selection
Ternary Operator$result = (condition) ? value1 : value2;Shorthand for if/else
Function Declarationfunction myFunc($param) { ... }Defines reusable code
Indexed Array$arr = array(1,2,3);Numeric keys automatically assigned
Associative Array$assoc = array("key" => "value");Key-value pairs
Constantsdefine("NAME", "value");Defines a constant value
String Concatenation$str = "Hello" . " World";Uses the dot operator
Type Casting(int)$var, (string)$varConverts variable types
Null Coalescing Operator$var = $a ?? 'default';Returns left operand if set, else default
Superglobals$_GET, $_POST, $_SERVER, $_SESSIONPredefined global arrays
File Inclusioninclude 'file.php';
require 'file.php';		Inserts external PHP files
Class Declarationclass MyClass { ... }Defines an object-oriented class
Interfacesinterface MyInterface { public function myMethod(); }Contracts for classes
Traitstrait MyTrait { ... }Reusable sets of methods
Anonymous Functions$func = function($x) { return $x * 2; };Functions without a name (closures)
Arrow Functions$fn = fn($x) => $x + 1;Shorter syntax for closures (PHP 7.4+)
Error Handlingtry { ... } catch (Exception $e) { ... }Manages exceptions
Sessionssession_start(); $_SESSION['user'] = 'Alice';Maintains user state
Cookiessetcookie("name", "value", time()+3600);Stores data on the client
Regular Expressionspreg_match('/pattern/', $string, $matches);Pattern matching in strings
PDO (PHP Data Objects)$pdo = new PDO($dsn, $user, $pass);Database access abstraction layer
JSON Functionsjson_encode($data); json_decode($json);Convert between JSON and PHP arrays/objects
Date & Time Functionsdate("Y-m-d"); time();Formats dates and gets the current timestamp
TermExplanation
PHP Opening Tag Every PHP script begins with the <?php tag and ends with ?>. These tags indicate to the server that the enclosed code should be executed as PHP. They are required at the beginning and end of your PHP code blocks.
Echo Statement The echo statement outputs one or more strings to the browser. For example, echo "Hello, World!"; will display the text. It’s one of the simplest ways to send output from your PHP code.
Variables Variables in PHP are declared with a dollar sign ($) followed by the variable name. PHP is loosely typed, so you do not have to declare a variable’s data type. For example, $name = "Alice"; stores a string, while $age = 30; stores an integer.
Comments Use // for single-line comments and /* ... */ for multi-line comments. Comments are ignored during execution and are used to explain your code.
Conditionals (If/Else) Conditional statements allow you to execute code based on a condition. For example, if ($x > 0) { ... } else { ... } executes different code blocks depending on whether $x is positive.
For Loop A for loop repeats a block of code a specific number of times. For example, for ($i = 0; $i < 10; $i++) { ... } runs the loop 10 times. It is commonly used when the number of iterations is known.
While Loop A while loop continues to execute as long as its condition remains true. For example, while ($x < 10) { ...; $x++; } will run until $x reaches 10.
Do-While Loop The do-while loop executes the code block once and then repeats it as long as the condition is true. It ensures that the loop is executed at least once.
Foreach Loop The foreach loop iterates over each element in an array. For example, foreach ($array as $value) { ... } processes each item in the array sequentially.
Switch Statement The switch statement compares a variable against multiple cases and executes the corresponding block. For example, switch($var) { case 'a': ... break; default: ... } is useful for handling multiple conditions.
Ternary Operator The ternary operator offers a shorthand way to write an if/else statement. For example, $result = ($x > 0) ? 'positive' : 'non-positive'; assigns a value based on the condition.
Function Declaration Functions are defined with the function keyword. They encapsulate code for reuse. For example, function add($a, $b) { return $a + $b; } creates a function that adds two numbers.
Arrays PHP supports both indexed and associative arrays. Indexed arrays use numeric keys (e.g., $arr = array(1,2,3);), while associative arrays use named keys (e.g., $person = array("name" => "Alice", "age" => 30);).
Constants Constants are defined using the define() function. For example, define("SITE_NAME", "My Website"); creates a constant that cannot be changed during script execution.
String Concatenation PHP concatenates strings using the dot operator. For example, $greeting = "Hello" . " " . "World!"; joins multiple strings into one.
Type Casting You can convert a variable’s type by casting it. For example, (int)$var casts a variable to an integer. This is useful when you need to ensure a variable is of a specific type.
Null Coalescing Operator The null coalescing operator (??) returns the left-hand operand if it exists and is not null; otherwise, it returns the right-hand operand. For example, $value = $data['key'] ?? 'default';
Superglobals Superglobals are built-in arrays accessible in any scope. Common examples include $_GET, $_POST, $_SERVER, and $_SESSION.
File Inclusion Use include or require to incorporate external PHP files. For example, require 'header.php'; embeds the contents of header.php.
Classes & Objects Define a class with class ClassName { ... } and instantiate it with $obj = new ClassName();. Object-oriented programming helps structure code into reusable blueprints.
Interfaces Interfaces define methods that classes must implement. For example, interface Logger { public function log($msg); } forces implementing classes to define the log() method.
Traits Traits allow you to reuse methods across multiple classes. For example, trait MyTrait { function sayHi() { echo "Hi"; } } can be included in any class using the use keyword.
Anonymous Functions These are functions without a name, often used as callbacks. For example, $func = function($x) { return $x * 2; };
Arrow Functions Introduced in PHP 7.4, arrow functions provide a shorter syntax for anonymous functions. For example, $fn = fn($x) => $x + 1;
Error Handling Use try { ... } catch (Exception $e) { ... } to handle exceptions and errors gracefully, ensuring that your application can manage unexpected issues.
Sessions Sessions store user data between page requests. Start a session with session_start(); and use the $_SESSION superglobal to store and retrieve data.
Cookies Set cookies using setcookie("name", "value", time()+3600); to store small amounts of data on the client side.
Regular Expressions PHP supports regex functions like preg_match() and preg_replace() for pattern matching in strings.
PDO (PHP Data Objects) PDO provides a uniform method to access databases. For example, $pdo = new PDO($dsn, $user, $pass); establishes a database connection.
JSON Functions Convert PHP arrays and objects to JSON with json_encode() and back with json_decode(). These functions are essential for API development.
Date & Time Functions Functions like date() and time() are used to format dates and retrieve the current timestamp. For example, date("Y-m-d") returns today’s date.