Send PHP errors to default error log plus user-defined error log

Solution:1

You can set your own error handler and still let php handle the triggered error as usual

http://se.php.net/manual/en/function.set-error-handler.php

set_error_handler(function($errno, $errstr, $errfile, $errline) {
  // do what you want  
  return false; // returning false makes PHP execute its own error handler as well
});

Solution:2

You can use custom error handler and log message into different files like that,

    function myErrorHandler($errno, $errstr, $errfile, $errline)
    {
        if (!(error_reporting() & $errno)) {
            return false;
        }
        $logFile = "";
        switch ($errno) {
        case E_USER_ERROR:
            $logFile = "logs/php-errors-".date("yyyy-mm-dd",time());
            exit(1);
            break;

        case E_USER_WARNING:
        $logFile = "logs/php-warnings-".date("yyyy-mm-dd",time());
            break;

        case E_USER_NOTICE:
        $logFile = "logs/php-notices-".date("yyyy-mm-dd",time());
            break;

        default:
        $logFile = "logs/php-unkown-".date("yyyy-mm-dd",time());
            break;
        }

      error_log($errstr,3,$logFile);
        return true;
    }

and you should set this error handler function using

    set_error_handler("myErrorHandler");