PHPの exit()では終了コードを指定できるらしい

PHP: exit - Manual

If status is an integer , that value will be used as the exit status and not printed. Exit statuses should be in the range 0 to 254, the exit status 255 is reserved by PHP and shall not be used. The status 0 is used to terminate the program successfully.

問題無しの場合はゼロを指定すると。呼び出し側でStatusを判断できるなら渡してあげると正しい使い方なわけだ。
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