Why Does `localhost` and `127.0.0.1` Behave Differently in PHP\'s `mysql_connect()`?

Why does localhost and 127.0.0.1 behave differently in PHP's mysql_connect()?

Does using localhost in mysql_connect() make the connection faster than using 127.0.0.1?

The speed difference between using localhost and 127.0.0.1 in mysql_connect() depends on the operating system.

On Windows, mysql_connect() uses TCP/IP by default, regardless of whether localhost or 127.0.0.1 is used. Therefore, there is no speed difference between the two options on Windows.

On Linux, however, mysql_connect() tries to use a Unix domain socket if localhost is specified, and TCP/IP if 127.0.0.1 is specified. A Unix domain socket is a local communication mechanism that is faster than TCP/IP because it avoids the network overhead. Therefore, using localhost can be slightly faster than using 127.0.0.1 on Linux.

What is the connection type between the PHP script and MySQL (when using the mysql_connect() function)? Is it TCP/IP?

As mentioned above, the connection type depends on the operating system and which hostname is used.

On Windows, mysql_connect() always uses TCP/IP.
On Linux, mysql_connect() uses a Unix domain socket if localhost is specified, and TCP/IP if 127.0.0.1 is specified.

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