How php throws an error

//调试 php报错
    function socketErrorLog($errno, $errstr, $errfile, $errline)
    {
        $log = '[' . date('m d H:i:s') . '] errno:' . $errno . " errfile:$errfile line:$errline\n";
        $log .= "error: " . $errstr;
        $log .= "\n========================================================\n";
        file_put_contents(dirname(__FILE__).'/chaoyu.log', $log, FILE_APPEND);
    }
//抛出php错误
set_error_handler('socketErrorLog');