You can try creating a helper function like this:
// Helper function
function getLike($str, $deliminator = ';', $field = 'kategorien') {
if (false !== strpos($str, $deliminator)) {
$strParts = explode($deliminator, $str);
return "($field LIKE '%". implode("%' OR $field LIKE '%", $strParts) . "%')";
} else {
return "$field LIKE '%$str%'";
}
}
// Debug
var_dump(getLike('1;6;14;16'));
Outputs:
string '(kategorien LIKE '%1%' OR kategorien LIKE '%6%' OR kategorien LIKE '%14%' OR kategorien LIKE '%16%')' (length=100)
In your query, you'd use it like this:
"SELECT * FROM tbl WHERE ". getLike($_GET['katid']) ." AND status = 1 ORDER BY pos ASC"