I'm going to step up and say wontfix on this.

The main problem here is that PHP isn't designed to work in a way where it can syntactically validate code and not allow that code to impact the runtime as well. There are assorted performance enhancements and features that assume code being inspected is supposed to be (potentially) executed. For example, class and function definitions are normally hoisted and that happens before any code is executed.

Refactoring PHP to support another interstitial layer where code is validated before anything gets interpreted seems to me like a lot of effort for little gain. Consider that you can already `php -l` a file, plus there are third-party libraries out there that are made to do this.

While it's definitely not a good suggestion, note that create_function is basically just a wrapper around eval()ing a function definition so if you don't mind ignoring common sense then there's not much to stop you from doing
  eval('function() { ?>' . preg_replace(['|use [\w,\s\\\\]*;|'], '', $code) . '<?php };');

If you feel strongly about adding something that can be accessed from PHP code, check out the RFC process.
  https://wiki.php.net/rfc
(though the mailing lists are down...)

* https://wiki.php.net/rfc/howto

is there any advice on how to check syntax inside php?

For user contributed code, I really want to check the syntax before using the code.

sorry, I didn't see your comment.
You're right, eval solves my problem.

I thought eval solves the problem, but it is not. The changed behaviour of eval "Before PHP 7, in this case eval() returned FALSE and execution of the following code continued normally. It is not possible to catch a parse error in eval() using set_error_handler()."
makes it impossible to check for syntax errors and handle them apropriate!

> makes it impossible to check for syntax errors and handle them apropriate!
Thank you for reading the documentation, but while the sentence you identified does explain that you can no longer handle parse errors with set_error_handler(), the sentence immediately before it told you the new behavior:

> As of PHP 7, if there is a parse error in the evaluated code, eval() throws a
> ParseError exception.

this is simply not true because with try-catch you have everything you need without the drawback of mangle with the error handler

Test-Script:
<?php

function shutdown(){
	echo 'shutdown';
}

register_shutdown_function('shutdown');
$code = '?;';

try{
	$var = eval('function() { ?>' . preg_replace(['|use [\w,\s\\\\]*;|'], '', $code) . ' <?php } ?>');
} catch (Exception $e){
	echo 'exception catched';
	print_r($e);
}


$php -v
PHP 7.2.11 (cli) 

$php test.php 
shutdown


=> I get no exception to catch!

because your code is simply wrong

catch(Throwable $e)
{ 
}

same output for
Throwable

it works, period, refactor and simplify your code, you can catch parse errors as any other exception, starzing with PHP7 "Throwable"catches *anything* and if that don't happen you have other problems - this is a bugtracker and not a support forum


---------------------------

[harry@srv-rhsoft:/downloads]$ php test.php
exception catchedParseError Object
(
    [message:protected] => syntax error, unexpected end of file
    [string:Error:private] =>
    [code:protected] => 0
    [file:protected] => /mnt/data/downloads/test.php(4) : eval()'d code
    [line:protected] => 1
    [trace:Error:private] => Array
        (
        )

    [previous:Error:private] =>
)

---------------------------

[harry@srv-rhsoft:/downloads]$ cat test.php
<?php
try
{
 $var = eval('nonsense');
}
catch (Throwable $e)
{
 echo 'exception catched';
 print_r($e);
}

sorry, found my mistake in the testcode :(

Throwable was the solution I didn't see.

Thanks for pointing it out, sorry to bother you.

don't get me wrong but "Throwable was the solution I didn't see" is a strange response after "same output for Throwable"

I wanted to say "Throwable" solved it. 

But I didn't recognize it as a solution, since I'd simplified my code and by doing this there was no error that could be catched. And finally the shutdown function was correctly executed, since the program ends. In real code this does not happen. I was mixing up real code and demo code.

Still thank you for your time.