php如何抛出错误

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