syntax error in valid if statement - php

Question

I have a PHP method which retrieves data either from memcache, or from the database if it is not yet available there.
Sometimes the data must be loaded from the DB to update the memcache, for example if something changes.
public function get_likes_per_user($u_id, $force_db = false) {
if ($this->memcache) {
$u_id = intval($u_id);
$key = 'liked_news_' . $u_id;
$res = $this->memcache->get($key);
if ($res != '') {
$res = unserialize($res);
}
// This line causes a syntax error for no obvious reason
if(!is_array($res) || $force_db){
$res = array();
$sql = "...";
$uu_query = $this->datenbank->query_result($sql);
while ($row = $uu_query->fetch_row()) {
$res[] = $row['uu_id'];
}
$this->memcache->set($key, serialize($res), 0, 3600);
}
return $res;
} else {
throw new Exception("Kein Memcache Objekt!");
}
}
For some reason I don't understand php decides to throw a syntax error for the if statement which decides whether or not to reload the data from the DB.
I tried different notations for this statement but I can't figure out what causes the error.
Did anyone encounter something similar?
PHP Version 5.4
UPDATE:
I've found the cause of the error. I am working on a mac and to write a pipe charakter you have to press alt+7. If you press alt+spacebar mac OS X will insert a non-breaking space, which is invalid for PHP. So my mistake was to keep alt pressed after typing the two pipes for the OR statement.