PHP Cheat Sheet

Here's a PHP cheat sheet covering the essentials:

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Basic Syntax

• Echo / Print:

    echo "Hello, World!";
    print "Hello, World!";
  

• Variables:

    $variable = "Hello!";
  

• Comments:

    // Single-line comment
    # Single-line comment
    /* Multi-line 
       comment */
  

Data Types

• String:

    $string = "Hello, World!";
  

• Integer:

    $integer = 42;
  

• Float:

    $float = 3.14;
  

• Boolean:

    $bool = true;
  

• Array:

    $array = ["apple", "banana", "cherry"];
  

• Associative Array:

    $assocArray = ["name" => "John", "age" => 30];
  

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Strings

• String Concatenation:

    $greeting = "Hello, " . "World!";
  

• String Interpolation:

    $name = "John";
    echo "Hello, $name!";
  

• String Length:

    echo strlen("Hello");
  

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Arrays

• Indexed Array:

    $colors = ["red", "green", "blue"];
  

• Associative Array:

    $person = ["name" => "Alice", "age" => 25];
  

• Multidimensional Array:

    $matrix = [
        [1, 2, 3],
        [4, 5, 6],
        [7, 8, 9]
    ];
  

• Array Functions:

    array_push($colors, "yellow");  // Add element
    array_pop($colors);             // Remove last element
    count($colors);                 // Count elements
  

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Control Structures

• If-Else:

    if ($a > $b) {
        echo "a is greater than b";
    } elseif ($a == $b) {
        echo "a is equal to b";
    } else {
        echo "a is less than b";
    }
  

• Switch:

    $color = "red";
    switch ($color) {
        case "red":
            echo "Color is red";
            break;
        case "blue":
            echo "Color is blue";
            break;
        default:
            echo "Unknown color";
    }
  

• For Loop:

    for ($i = 0; $i < 10; $i++) {
        echo $i;
    }
  

• Foreach Loop:

    foreach ($array as $value) {
        echo $value;
    }
  

• While Loop:

    while ($i < 10) {
        echo $i;
        $i++;
    }
  

• Do-While Loop:

    do {
        echo $i;
        $i++;
    } while ($i < 10);
  

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Functions

• Define a Function:

    function greet($name) {
        return "Hello, $name!";
    }
  

• Function with Default Parameter:

    function greet($name = "World") {
        return "Hello, $name!";
    }
  

• Anonymous Function:

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

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Superglobals

• $_GET and $_POST:

    // Using GET
    $name = $_GET['name'];
  
    // Using POST
    $email = $_POST['email'];
  

• $_SESSION and $_COOKIE:

    // Start Session
    session_start();
    $_SESSION['username'] = 'JohnDoe';
  
    // Set Cookie
    setcookie("user", "JohnDoe", time() + (86400 * 30), "/");
  

• $_SERVER:

    echo $_SERVER['PHP_SELF']; // Current file name
    echo $_SERVER['SERVER_NAME']; // Server name
  

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File Handling

• Open a File:

    $file = fopen("file.txt", "r");
  

• Read a File:

    $content = fread($file, filesize("file.txt"));
  

• Write to a File:

    $file = fopen("file.txt", "w");
    fwrite($file, "Hello, World!");
    fclose($file);
  

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Database (MySQLi)

• Connect to Database:

    $conn = new mysqli("localhost", "username", "password", "database");
  

• Check Connection:

    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
  

• Select Data:

    $result = $conn->query("SELECT * FROM table");
    while($row = $result->fetch_assoc()) {
        echo $row['column_name'];
    }
  

• Insert Data:

    $sql = "INSERT INTO table (column1, column2) VALUES ('value1', 'value2')";
    $conn->query($sql);
  

• Close Connection:

    $conn->close();
  

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Error Handling

• Try-Catch Block:

    try {
        // Code that may throw an exception
        throw new Exception("An error occurred");
    } catch (Exception $e) {
        echo "Error: " . $e->getMessage();
    }
  

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Date and Time

• Current Date and Time:

    echo date("Y-m-d H:i:s");
  

• Format Date:

    $date = date("l, d-M-Y");
  

• Get Timestamp:

    echo time();
  

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Object-Oriented Programming (OOP)

• Define a Class:

    class Car {
        public $color;
  
        function __construct($color) {
            $this->color = $color;
        }
  
        function getColor() {
            return $this->color;
        }
    }
  
    $myCar = new Car("red");
    echo $myCar->getColor();
  

• Inheritance:

    class Vehicle {
        protected $brand;
        public function __construct($brand) {
            $this->brand = $brand;
        }
    }
  
    class Car extends Vehicle {
        public function getBrand() {
            return $this->brand;
        }
    }
  

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Miscellaneous

• Define a Constant:

    define("SITE_NAME", "My Website");
    echo SITE_NAME;
  

• PHP Info:

    phpinfo();
  

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