Throwable work on PHP 7.x. 

Exception work on PHP 5.x. 

 参考链接： https://www.php.net/manual/en/language.errors.php7.php

​<?php

try {

  // Code that may throw an Exception or Error.

} catch (Throwable $t) {

  // Executed only in PHP 7, will not match in PHP 5

} catch (Exception $e) {

  // Executed only in PHP 5, will not be reached in PHP 7

}