PHP OR运算符有问题吗？

Question

My dump variables appear on their pages:

if ($_SERVER['REMOTE_ADDR'] == '44.71.45.98' OR '44.71.45.99') {
  //blah blah
}else{
  //blah
}

I know this is wrong but when I tried..it's working to my another computer.It didn't prompt me an error even if i know that this is wrong...

Usually I code or like these:

//this is correct
if(isset($a) or isset($b)){

}