<?php
$String = "[b][color=#0000ff]TEST[/color][/b]";
$regex = '|[[\/\!]*?[^\[\]]*?]|si';
$String = preg_replace($regex, '', $String);
print $String."\n";
?>
Reference: https://forum.proxmox.com/threads/proxmox-ve-screen-out-of-range.131297/