Top 50 PHP Interview Questions and Answer

PHP is a widely used programming language for web development. If you're preparing for a PHP job interview, having a strong grasp of key concepts is essential. In this article, we’ll explore the top 50 PHP interview questions and answers to help you confidently succeed in your next interview. 

  Q1. What is PHP?

Answer: PHP stands for Hypertext Preprocessor. It is an open-source, server-side scripting language designed for creating dynamic web pages.

Q2. What are the common uses of PHP?

Answer: PHP is commonly used for:

• Server-side scripting
• Command-line scripting
• Creating dynamic websites
• Interacting with databases (e.g., MySQL)
• Building RESTful APIs

Q3. How do you declare a variable in PHP?

Answer: Variables are declared using the $ symbol, e.g., $name = "Waliullah";.

Q4. What are PHP data types?

Answer : PHP supports:

• String
• Integer
• Float (Double)
• Boolean
• Array
• Object
• NULL
• Resource

Q5. What is the difference between echo and print?

Answer:

• echo: Outputs data, can take multiple parameters, no return value.
• print: Outputs data, returns 1, works like a function.

Q6. How do you define a constant in PHP?

Answer: Using the define() function, e.g., define("SITE_NAME", "Shikshatech");.

Q7. What are PHP magic constants?

Answer: Special constants starting with double underscores, like:

• __LINE__
• __FILE__
• __DIR__
• __FUNCTION__
• __CLASS__

Q8. What is the difference between == and ===?

Answer:

• ==: Compares values only.
• ===: Compares values and data types.

Q9. What are superglobals in PHP?

Answer: 

Predefined global arrays like 

• $_POST, 
• $_GET, 
• $_SESSION, 
• $_COOKIE, 
• $_SERVER.

 Q10. How to connect to a MySQL database using PHP?

Answer:

To connect to a MySQL database using PHP, you can use either the MySQLi (MySQL Improved) extension or PDO (PHP Data Objects). Here's how to do it both ways:

Using MySQLi (Object-Oriented Style)

<?php

$host = "localhost";
$username = "your_username";
$password = "your_password";
$database = "your_database";

// Create connection
$conn = new mysqli($host, $username, $password, $database);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>


Using MySQLi (Procedural Style)

<?php
$host = "localhost";
$username = "your_username";
$password = "your_password";
$database = "your_database";

// Create connection
$conn = mysqli_connect($host, $username, $password, $database);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>


Using PDO (Recommended for Flexibility and Security)

<?php
$host = 'localhost';
$db   = 'your_database';
$user = 'your_username';
$pass = 'your_password';
$charset = 'utf8mb4';

$dsn = "mysql:host=$host;dbname=$db;charset=$charset";

try {
    $pdo = new PDO($dsn, $user, $pass);
    // Set error mode to exception
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>