Database: Ensure MySQL port numbers are numeric in wpdb.

Ensure the database port number is recorded as an integer or `null` (the default port) when parsing the database host.

This is to prevent PHP/MySQLi throwing an exception caused by ports represented as numeric strings.

Props audrasjb, azouamauriac, chaion07, costdev, johnjamesjacoby, jrf, sergeybiryukov.
Fixes #54877.


git-svn-id: https://develop.svn.wordpress.org/trunk@53670 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/wp-db.php

@@ -2077,6 +2077,9 @@ class wpdb {
 			}
 		}
 
+		// MySQLi port cannot be a string; must be null or an integer.
+		$port = $port ? absint( $port ) : null;
+
 		return array( $host, $port, $socket, $is_ipv6 );
 	}