Basic PHP Questions

1. What is PHP?
   PHP (Hypertext Preprocessor) is a server-side scripting language used for web development.

2. What are the key features of PHP?

   • Open-source
   • Cross-platform
   • Embedded in HTML
   • Supports databases
   • Loosely typed

3. What is the default file extension for PHP files?
   .php

4. How do you print text in PHP?

   echo "Hello, World!";
   

5. How do you start and end a PHP script?

   <?php 
   // PHP code
   ?>
   

6. How do you write comments in PHP?

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

7. What are PHP variables?
   Variables store data and begin with $, e.g., $name = "John";

8. How do you concatenate strings in PHP?

   $fullName = $firstName . " " . $lastName;
   

9. How do you declare a constant in PHP?

   define("SITE_NAME", "MyWebsite");
   

10. What are PHP data types?

    • String
    • Integer
    • Float
    • Boolean
    • Array
    • Object
    • NULL
    • Resource

Control Structures

11. What is an if statement in PHP?

    if ($age > 18) {
        echo "You are an adult.";
    }
    

12. What is an else statement?

    if ($age > 18) {
        echo "Adult";
    } else {
        echo "Minor";
    }
    

13. How does switch work in PHP?

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

14. What is a while loop?

    while ($x < 5) {
        echo $x;
        $x++;
    }
    

15. What is a for loop?

    for ($i = 0; $i < 5; $i++) {
        echo $i;
    }
    

16. What is a foreach loop?

    $arr = ["apple", "banana", "cherry"];
    foreach ($arr as $fruit) {
        echo $fruit;
    }
    

17. What is a do-while loop?

    do {
        echo $x;
        $x++;
    } while ($x < 5);
    

18. What is the difference between break and continue?

    • break exits the loop.
    • continue skips the current iteration and proceeds to the next.

Functions

19. How do you define a function in PHP?

    function greet() {
        return "Hello!";
    }
    

20. How do you pass arguments to a function?

    function add($a, $b) {
        return $a + $b;
    }
    

21. What are default function arguments?

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

22. What is variable scope in PHP?

    • Local
    • Global
    • Static

23. What is a recursive function?

    function factorial($n) {
        if ($n == 0) return 1;
        return $n * factorial($n - 1);
    }
    

Arrays

24. How do you create an array in PHP?

    $arr = [1, 2, 3];
    

25. What is an associative array?

    $user = ["name" => "John", "age" => 25];
    

26. What is a multidimensional array?

    $matrix = [[1, 2], [3, 4]];
    

27. How do you count elements in an array?

    count($arr);
    

28. How do you sort an array?

    sort($arr);
    

String Handling

29. How do you find the length of a string?

    strlen("Hello");
    

30. How do you convert a string to uppercase?

    strtoupper("hello");
    

31. How do you replace a substring?

    str_replace("world", "PHP", "Hello world");
    

File Handling

32. How do you open a file in PHP?

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

33. How do you write to a file?

    fwrite($file, "Hello, World!");
    

34. How do you read from a file?

    fread($file, filesize("test.txt"));
    

Database Handling (MySQL with PHP)

35. How do you connect to a MySQL database in PHP?

    $conn = mysqli_connect("localhost", "root", "", "test_db");
    

36. How do you insert data into a MySQL database?

    $sql = "INSERT INTO users (name, email) VALUES ('John', 'john@example.com')";
    mysqli_query($conn, $sql);
    

37. How do you fetch data from a MySQL database?

    $result = mysqli_query($conn, "SELECT * FROM users");
    while ($row = mysqli_fetch_assoc($result)) {
        echo $row['name'];
    }
    

Security

38. What is SQL Injection?
    SQL injection is a hacking technique that exploits vulnerabilities in database queries.

39. How do you prevent SQL injection?
    Use prepared statements:

    $stmt = $conn->prepare("SELECT * FROM users WHERE email = ?");
    $stmt->bind_param("s", $email);
    

40. How do you hash passwords in PHP?

    password_hash("mypassword", PASSWORD_BCRYPT);
    

Advanced Topics

41. What is an API in PHP?
    An API (Application Programming Interface) allows PHP to interact with external services.

42. What is cURL in PHP?
    A tool for making HTTP requests.

43. How do you use cURL in PHP?

    $ch = curl_init("https://api.example.com");
    curl_exec($ch);
    

Sessions and Cookies

44. What is a session in PHP?
    A session stores user data across multiple pages.

45. How do you start a session in PHP?

    session_start();
    

46. How do you set a session variable?

    $_SESSION["user"] = "John";
    

47. How do you destroy a session?

    session_destroy();
    

48. What is a cookie in PHP?
    A cookie is a small piece of data stored on the user's browser.

49. How do you set a cookie?

    setcookie("username", "John", time() + 3600);
    

50. How do you retrieve a cookie?

    echo $_COOKIE["username"];
    

51. How do you delete a cookie?

    setcookie("username", "", time() - 3600);
    

Object-Oriented Programming (OOP) in PHP

52. What is OOP in PHP?
    OOP allows you to structure code using classes and objects.

53. How do you define a class in PHP?

    class Car {
        public $color;
    }
    

54. How do you create an object from a class?

    $myCar = new Car();
    

55. What is a constructor in PHP?

    class Car {
        function __construct() {
            echo "Car is created!";
        }
    }
    

56. What is inheritance in PHP?

    class Vehicle {}
    class Car extends Vehicle {}
    

57. What are public, private, and protected access modifiers?

    • public: Accessible anywhere
    • private: Accessible only within the class
    • protected: Accessible within the class and subclasses

58. What is method overriding in PHP?
    A child class can override a method of a parent class.

59. What is an interface in PHP?

    interface Vehicle {
        public function drive();
    }
    

60. What is an abstract class?

    php
    CopyEdit
    abstract class Animal {
        abstract public function makeSound();
    }
    

61. What is a trait in PHP?

    trait Logger {
        public function log($msg) {
            echo $msg;
        }
    }
    

Error Handling

62. How do you handle errors in PHP?

    try {
        throw new Exception("Error occurred");
    } catch (Exception $e) {
        echo $e->getMessage();
    }
    

63. What are the types of errors in PHP?

    • Notice
    • Warning
    • Fatal Error
    • Parse Error

64. How do you turn off error reporting?

    error_reporting(0);
    

65. How do you log errors to a file?

    ini_set("log_errors", 1);
    ini_set("error_log", "errors.log");
    

PHP and AJAX

66. How do you send an AJAX request to a PHP script?
    Use JavaScript’s fetch() or jQuery’s $.ajax().

67. How do you handle an AJAX request in PHP?

    echo json_encode(["message" => "Hello from PHP"]);
    

PHP Frameworks

68. What is Laravel?
    A PHP framework for web development.

69. What is CodeIgniter?
    A lightweight PHP framework.

70. What is Symfony?
    A high-performance PHP framework for enterprise projects.

Security in PHP

71. How do you prevent XSS (Cross-Site Scripting)?

    htmlspecialchars($input, ENT_QUOTES, "UTF-8");
    

72. What is CSRF (Cross-Site Request Forgery)?
    An attack where unauthorized commands are executed on behalf of a user.

73. How do you prevent CSRF?
    Use CSRF tokens in forms.

PHP File Upload

74. How do you upload a file in PHP?

    move_uploaded_file($_FILES["file"]["tmp_name"], "uploads/" . $_FILES["file"]["name"]);
    

PHP JSON Handling

75. How do you encode an array into JSON?

    json_encode($array);
    

76. How do you decode JSON into an array?

    json_decode($json, true);
    

PHP Date and Time

77. How do you get the current date and time in PHP?

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

78. How do you get the timestamp in PHP?

    time();
    

79. How do you modify a date?

    echo date("Y-m-d", strtotime("+1 week"));
    

PHP Email Handling

80. How do you send an email in PHP?

    mail("user@example.com", "Subject", "Message");
    

Miscellaneous Questions

81. What is the difference between == and === in PHP?

    • == checks value equality
    • === checks both value and type

82. What is the difference between include and require?

    • include gives a warning if the file is missing
    • require gives a fatal error if the file is missing

83. How do you redirect in PHP?

    header("Location: home.php");
    

84. How do you destroy a PHP script?

    die("Terminated");
    

85. How do you access form data in PHP?

    $_POST["name"];
    

86. How do you start a PHP CLI script?

    #!/usr/bin/php
    

87. What is explode() in PHP?

    explode(",", "apple,banana,cherry");
    

88. What is implode() in PHP?

    implode("-", ["apple", "banana"]);
    

89. What is isset()?
    Checks if a variable is set.

90. What is empty()?
    Checks if a variable is empty.

91. What is unset()?
    Deletes a variable.

92. What is strip_tags()?
    Removes HTML tags from a string.

93. What is nl2br()?
    Converts newlines to <br>.

94. What is array_merge()?
    Merges arrays.

95. What is array_push()?
    Adds an element to an array.

96. What is array_pop()?
    Removes the last element of an array.

97. What is file_get_contents()?
    Reads a file into a string.

98. What is file_put_contents()?
    Writes a string to a file.

99. What is session_unset()?
    Removes all session variables.

100. How do you run a PHP script from the command line?
     bash php script.php