Five Common PHP Interview Questions with Brief Explanations

If you’re preparing for a PHP developer interview — whether for your first job, internship, or freelance role — being familiar with core PHP concepts is essential. Below are five commonly asked PHP interview questions along with brief explanations to help you answer confidently and accurately.

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1️⃣ What is the difference between include() and require() in PHP?

Explanation:
Both include() and require() are used to include files in PHP, but they behave differently on error:

• include() shows a warning and continues executing the script.
• require() shows a fatal error and stops the script if the file is missing.

🧠 Tip: Use require() for critical files like database connections.

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2️⃣ What are GET and POST methods in PHP?

Explanation:
These are the two most common methods to send data to the server:

• GET: Sends data via the URL (visible), limited data capacity. Used for searches or filters.
• POST: Sends data in the request body (invisible), used for sensitive info like login forms.

🧠 Tip: Use POST when handling forms with passwords or personal data.

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3️⃣ What is the difference between == and === in PHP?

Explanation:

• == checks if values are equal (type is not considered).
• === checks if values and types are equal.

Example:

phpCopyEdit5 == "5"     // true
5 === "5"    // false

🧠 Tip: Use === for stricter, bug-free comparison in conditions.

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4️⃣ How do you connect to a MySQL database using PHP?

Explanation:
You can connect using mysqli or PDO. Here’s a basic example using mysqli:

phpCopyEdit$conn = mysqli_connect("localhost", "username", "password", "database");
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

🧠 Tip: Always handle connection errors and secure credentials.

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5️⃣ What is a session in PHP?

Explanation:
A session is a way to store user data (like login status) across multiple pages. PHP uses $_SESSION to track user information.

phpCopyEditsession_start();
$_SESSION['username'] = "admin";

🧠 Tip: Use sessions to manage user login systems and secure authentication.

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✅ Final Tip:

Practice writing code snippets for each of these concepts — and be ready to explain how and where you would use them in real-world projects.