Some examples...
MySQLi Connect
$mysqli = new mysqli('host', 'user', 'password', 'database');
PDO Connect
$pdo = new PDO("mysql:host=localhost;dbname=database", 'username', 'password');
MySQLi Query
$mysqli->query("INSERT INTO tabel (name) VALUES ('Peter')");
PDO Query
$pdo->query("INSERT INTO tabel (name) VALUES ('Peter')");
MySQLi Commit
$mysqli->commit();
PDO Commit
$pdo->commit();
So, what's actually the difference between pdo and mysqli? To me it's quite the same when coding.. Any difference in speed/safety/etc. ?
Is there any difference in PDO and MySQLi OOP?
Yes.
Just start actually using it and you will see.
In general, the only difference is that mysqli is a some sort of construction material for the higher level DB access library and shouldn't be used as is. While PDO is already sort of such a library and can be used as is.
Did you use google? PHP.net offers a detailed page exactly about this topic.
http://php.net/manual/en/mysqlinfo.api.choosing.php
The differences are in the keys (comparing mysql functionality):
API supports non-blocking, asynchronous queries with mysqlnd: Mysqli yes, PDO no
Supports all MySQL 5.1+ functionality: Mysqli yes, PDO most
API supports Multiple Statements: Mysqli yes, PDO most
But the key difference between mysqli and PDO is, you can also use PDO as an interface for SQLITE, Oracle, MS-SQL..... Mysqli only is for mysql