Fatal errors not reported in vercel logs

[fascinated]

I have a few basic "route all requests to php"-style deployments on vercel, and I am noticing that when these deployments encounter a Fatal Error (for ex, some silly type issue like trying to read from a null as if it was an array ;p), the Fatal error message does not appear in the Vercel logs.

Has anyone else encountered this? Is there a workaround?

My only php.ini tweak is "display_errors = Off", which shouldn't affect this.

Using this simple vercel.json, for reference:

{
    "functions": {
        "api/*.php":
        {
            "runtime": "[email protected]",
            "maxDuration": 60
        }
    },
    "rewrites": [
        {"source": "/(.*)", "destination": "api/routes.php"}
    ]
}

[f3l1x]

Hi @fascinated, so far I didn't check Vercel logs for this type of exceptions, I must take a look.

[fascinated]

Thanks for the quick response <3.

Here's an example "fatal error" script, this will return 500 as expected, but the error itself will not be in the logs:

    $bad_var = null;
    if(in_array("test", $bad_var['not_array'])) { 
        echo "we shouldn't be here ;)";
    } else {
        echo "TEST OK: value not found";
    }

It's also worth noting that if you change this script to something like [below] such that there's some output before the fatal error, then Vercel will not report a 500 at all (and the logging behavior is the same). I sorta get why this is (200 header + output already sent), but if memory serves right, the common nginx/php-fpm setup would still produce an error in this case. Is this one a buffering issue specifically?

    $bad_var = null;
    echo "OK";
    if(in_array("test", $bad_var['not_array'])) { 
        echo "we shouldn't be here ;)";
    } else {
        echo "TEST OK: value not found";
    }

[f3l1x]

Under the hood, there is simple PHP built-in development server.

If you start your script like that php -S 0.0.0.0:8080 api/index.php you can see what is on stdout and what on stderr. Maybe it's wrong in built-in server.

[fascinated]

Yeah, I was thinking it's some stdout/stderr thing, but it seems all of the output from php -S just goes to stderr, so maybe there's something else.