Because the conditions were quite complicated I've broken each down to variables and then compare the result.
// this had a single =, needed a ==
$required = (substr_count($row['user_items'],"ß{$quest1required}Þ") == 1);
$item = (substr_count($row['user_items'], "ß{$quest1item}Þ") < 1);
$reward = (substr_count($row['user_items'], "ß{$quest1reward}Þ") < 1);
//removed the semi-colon from the end
if ($required && $item && $reward)
{
//do stuff
}