解决php错误抑制符@抑制的错误仍能被自定义错误函数捕获的问题

本段摘录自php manual

PHP supports one error control operator: the at sign (@). When prepended to an expression in PHP, any diagnostic error that might be >generated by that expression will be suppressed.

If a custom error handler function is set with set_error_handler(), it will still be called even though the diagnostic has been suppressed, as >such the custom error handler should call error_reporting() and verify that the @ operator was used in the following way:

大意是：在php中使用@符号抑制的错误，仍能触发使用set_error_handler设置的自定义错误处理函数，所以需要在自定义的错误处理函数中过滤掉那些被抑制的错误，代码如下：

<?php
function my_error_handler($err_no, $err_msg, $filename, $linenum) {
    if (!(error_reporting() & $err_no)) {
        return false; // Silenced
    }
    // ...
}
?>

被抑制的错误在进入这个函数时，error_reporting()的结果为0，所以整个函数会返回false，于是起到了过滤的作用。