localhost vs. 127.0.0.1 in MySQL: What\'s the Performance and Connection Difference?

localhost vs. 127.0.0.1 in mysql_connect(): Performance and Connection Type

When using the mysql_connect() function in PHP to establish a connection to a MySQL database, options arise between using "localhost" and "127.0.0.1" as the hostname. This raises questions about speed and the underlying connection type.

Speed Comparison

The performance difference between "localhost" and "127.0.0.1" depends on the operating system. On Windows, which natively uses TCP/IP, both "localhost" and "127.0.0.1" will result in a TCP/IP connection, yielding no significant speed difference.

On Linux, however, the default behavior differs. If "localhost" is used, it attempts to establish a Unix Domain Socket connection. This type of connection is generally faster than TCP/IP due to its lower overhead. However, specifying "127.0.0.1" on Linux forces the use of TCP/IP, which would be slightly slower.

Connection Type

The connection type between the PHP script and MySQL using mysql_connect() depends on the hostname specified.

• "localhost" on Linux: Unix Domain Socket (if available), otherwise TCP/IP
• "127.0.0.1" on all systems: TCP/IP

Unix Domain Sockets provide a more efficient inter-process communication mechanism within the same machine, while TCP/IP is used for connections across different devices or over networks.

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