端口号必须是一个单独的参数:

$link = mysqli_connect('host', 'user', 'pass', 'db', 5306);

I have some trouble connecting to a mysql server. I can connect using the linux terminal, so I know that my host, port, user, and password works. I cannot, however, connect using PHP.

PHP Version: 5.2.17

Server version: 5.5.27-log MySQL Community Server (GPL)

Here is a test code example:

<?php

$link = mysqli_connect('host.com:5306', 'user', 'pass', 'db');

/* check connection */

if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

if (!mysqli_query($link, "SET a=1")) {
    printf("Errormessage: %s\n", mysqli_error($link));
}

/* close connection */
mysqli_close($link);    

?>

Gives the following warning:

Warning: mysqli_connect() [function.mysqli-connect]: (HY000/2005): Unknown MySQL server host 'host.com:5306' (1) in /.../test.php on line 3

Connect failed: Unknown MySQL server host 'host.com:5306' (1)

Any ideas on what to do?

The port number must be a separate argument:

$link = mysqli_connect('host', 'user', 'pass', 'db', 5306);