[Bug]: Fatal errors in ddtrace.stub.php

[sleepyboy]

Bug report

ddtrace.stub.php causes fatal errors in PHP 8:

Fatal error: Type mixed cannot be marked as nullable since mixed already includes null in $PATH/vendor/datadog/dd-trace/ext/ddtrace.stub.php on line 801

PHP Fatal error:  Type mixed cannot be marked as nullable since mixed already includes null in $PATH/vendor/datadog/dd-trace/ext/ddtrace.stub.php on line 811

This can be fixed by changing signature from ?mixed $body = null to mixed $body = null.

Once these errors are fixed, there will be multiple undefined constant errors:

Fatal error: Uncaught Error: Undefined constant "DDTrace\Internal\UNKNOWN" in $PATH/vendor/datadog/dd-trace/ext/ddtrace.stub.php on line 841

Fatal error: Uncaught Error: Undefined constant "UNKNOWN" in $PATH/vendor/datadog/dd-trace/ext/ddtrace.stub.php on line 874

These can be fixed by adding something like that to corresponding namespaces:

const UNKNOWN = 0;

For instance, this would fix the first undefined constant error:

<?php
namespace DDTrace {
    const UNKNOWN = 0; // this should fix it

    /**
     * @var int
     * @cvalue DD_TRACE_DBM_PROPAGATION_DISABLED
     */
    const DBM_PROPAGATION_DISABLED = UNKNOWN;
   ....
}

How to reproduce:
Create a test PHP file (eg. test.php) and include the stub file:

<?php

include('vendor/datadog/dd-trace/ext/ddtrace.stub.php');

Execute the file from a command line using PHP 8:

php test.php

PHP version

8.3

Tracer or profiler version

1.4.2

Installed extensions

No response

Output of phpinfo()

No response

Upgrading from

No response

[bwoebi]

Hey @sleepyboy,

we just noticed that today and already fixed it in #2933, where we removed these extra question marks.

Thanks for reporting though!

[bwoebi]

These UNKNOWN constants are special placeholders of the arginfo generator (https://github.com/php/php-src/blob/master/build/gen_stub.php). We cannot change these or put UNKNOWN there, as that would have the stub generator create an actual UNKNOWN constant for dd-trace-php. If you look at stubs from php-src itself, you'll also find this UNKNOWN constant there.

I suppose, if you want to actually include the stubs directly, you'll have to define a dummy const UNKNOWN = 0; or similar, right before including.