What is the difference between MySQL, MySQLi and PDO?

Here is a concise answer to the PHP interview question "What is the difference between MySQL, MySQLi and PDO?":

MySQL vs MySQLi vs PDO

The main differences between the MySQL, MySQLi and PDO extensions in PHP are:

MySQL

• Oldest MySQL extension, deprecated since PHP 5.5 and removed in PHP 7
• Procedural API, not object-oriented
• Does not support prepared statements or multiple statements
• Vulnerable to SQL injection if not properly escaped

MySQLi

• Improved MySQL extension with object-oriented and procedural APIs
• Supports prepared statements, multiple statements, transactions
• Provides more advanced features like stored procedures
• Still MySQL-specific, not portable...