if condition holds true only for 0 when comparing it with string variable [duplicate]

Question

The output of the code below is "fail" but if we pass 1 to $b as $b=1 then it will give the output as "pass". Can anybody tell me why this if condition holds true only for 0?

<?php 
      $a="abcd"; 
      $b=0; 
      if($a == $b)
      {
         echo "fail";
      } 
      else
      { 
         echo "pass";
      }
?>

Answer 1

That is because of PHP type juggling with == operator. The full table is given here.