Método de busca binária (binary search) em PHP

buscaBinaria.php

<?php

function buscaBinaria($array, $e)
{
   $n = count($array);
   $low = 0;
   $mid;
   $high = $n - 1;
   while($low <= $high)
   {
      $mid = (int)(($high - $low) / 2) + $low;
     
      if($array[$mid] > $e)
        $high = $mid - 1;
      elseif($array[$mid] < $e)
        $low  = $mid + 1;
      else
        return (int)$mid;
   }
   return -1;
}
$arr = array(100, 200, 300, 400, 500);
return var_dump(buscaBinaria($arr, 600)); // saída -1