PHP MySQL Database

PHP MySQL Database

Using PHP with MySQL allows you to store, retrieve, update, and delete data from a database—this is the backbone of dynamic websites and web applications.

We’ll cover everything step by step, from connection to queries, with examples + interview questions.

What is PHP MySQL?

PHP → server-side scripting language
MySQL → relational database
PHP + MySQL = dynamic, data-driven websites

Examples: Login system, registration, e-commerce, admin panels

Ways to Connect PHP with MySQL

PHP provides two main APIs:

Method	Description	Usage
MySQLi	Improved MySQL	Most common
PDO	PHP Data Objects	More secure & flexible

We’ll focus mainly on MySQLi (interview + practical friendly)

Create MySQL Database

Create Table

PHP MySQL Connection (MySQLi)

Connection Code

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "testdb";

$conn = mysqli_connect($servername, $username, $password, $database);

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

<?php

$servername = "localhost";

$username = "root";

$password = "";

$database = "testdb";

$conn = mysqli_connect($servername, $username, $password, $database);

if (!$conn) {

die("Connection failed: " . mysqli_connect_error());

}

echo "Connected successfully";

Always check connection errors

Insert Data into MySQL

Fetch Data from Database

Fetch Multiple Records

Update Data

Delete Data

Always use WHERE to avoid deleting all rows.

Prepared Statements (Security – Very Important)

Protects against SQL Injection.

Mandatory for interviews & real projects

Close Database Connection

Frees server resources

MySQLi vs PDO (Interview Favorite)

Feature	MySQLi	PDO
Database support	MySQL only	Multiple DBs
Prepared statements	Yes	Yes
OOP support	Yes	Yes
Interview usage	Very common	Advanced

Common Mistakes

Not checking DB connection
Using plain queries (SQL injection risk)
Forgetting WHERE in UPDATE/DELETE
Not closing connection
Hardcoding credentials in public files

Interview Questions & MCQs (Very Important)

Q1. Which function connects PHP to MySQL?

A) mysql_connect()
B) mysqli_connect()
C) connect_mysql()
D) db_connect()

Answer: B

Q2. Which method is more secure?

A) Normal queries
B) Prepared statements

Answer: B

Q3. Which function fetches associative array?

A) mysqli_fetch()
B) mysqli_fetch_assoc()
C) mysqli_fetch_row()
D) mysqli_result()

Answer: B

Q4. What does PDO stand for?

A) PHP Data Object
B) PHP Database Option
C) Program Data Object
D) Private Data Object

Answer: A

Q5. Which SQL command retrieves data?

A) INSERT
B) UPDATE
C) SELECT
D) DELETE

Answer: C

Real-Life Use Cases

Login & registration system
CRUD applications
Admin dashboards
E-commerce websites
CMS systems

Summary

PHP + MySQL = dynamic websites
Use MySQLi or PDO
Always use prepared statements
Perform CRUD operations
Close DB connection
Core topic for PHP interviews & projects

PHP MySQL Database