In php4.3.0RC2:

When a new socket is created, the current error code for 
that socket is not initialized to 0.  I recommend that it 
should be.  The following code outputs:

error: 1313166380: Unknown error: 1313166380

The value changes from time to time.

<?php

if ($listener_sock = socket_create(AF_INET, SOCK_STREAM, 
SOL_TCP)) {
	if ($error_code = socket_last_error($listener_sock)) {
    echo "error: $error_code: " . socket_strerror 
($error_code)."\n";
	}
}


?>