Why is my PDO connection via TCP failing with a \'No such file or directory\' error referring to a Unix socket?

Warning: PDO Connection via TCP Fails with No Such File or Directory (unix:///tmp/mysql.sock)

In the midst of our coding endeavors, it's not uncommon to encounter perplexing exceptions that seem to emerge out of nowhere. Consider this scenario:

I'm attempting to connect to a database using PDO, but I'm getting this cryptic error message:

Warning: PDO::__construct(): [2002] No such file or directory (trying to connect via unix:///tmp/mysql.sock) in ...

Despite the specified TCP connection parameters, the system seems to be trying to connect via a Unix socket. It's imperative to rectify this issue to establish a stable database connection. So, what went wrong?

The Root of the Problem

The core issue lies in the interpretation of the hostname "localhost". By default, MySQL client libraries assume "localhost" refers to a Unix socket rather than a TCP hostname. To explicitly specify a TCP connection, you must use the IP address "127.0.0.1" instead of "localhost" as the hostname.

Alternatively, you can specify the Unix socket path explicitly in the DSN using the unix_socket parameter instead of the host parameter.

Resolving the Issue

To resolve this issue, ensure that you're using the correct hostname ("127.0.0.1") or specify the Unix socket path explicitly in the DSN. Additionally, check if the socket path is defined correctly in your php.ini file (if applicable).

Example DSN Using IP Address:

<code class="php">$dsn = 'mysql:host=127.0.0.1;port=3306;dbname=test';</code>

Example DSN Using Unix Socket Path:

<code class="php">$dsn = 'mysql:unix_socket=/tmp/mysql.sock;dbname=test';</code>

By implementing these adjustments, you can establish a stable database connection and mitigate the "No such file or directory" error effectively.

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