1 
     '; //输出查找流程11             12             if ($num == $arr[$mid]) {13                 return $mid;14             }elseif ($num > $arr[$mid]) {15                 $start = $mid + 1;16             } elseif ($num < $arr[$mid]) {17                 $end = $mid - 1;18             }19             $mid = floor(($start + $end) / 2);20         }21         return -1;22     }23     24     $search_arr = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);25     echo '4的索引值为:', search($search_arr, 4);