[RFC] Deprecate the extract function in PHP 7.3

Hi! The extract function takes an associative array and puts it into the local symbol table. http://php.net/manual/en/function.extract.php ``` $array = [     ‘foo’ => ‘foo’,     ‘bar’ => ‘bar’, ]; extract($array); print $foo; // "foo" ``` As a second parameter the extract function takes some options to make this function less dangerous, like EXTR_SKIP that prevents an existing local variable of being overwritten. There’s a few more options, go ahead and take a look at the documentation. EXTR_OVERWRITE is the default one though. You can also pass a prefix for the variable names as a third argument. I seriously doubt the usefulness of this function, especially looking at the potential risks. The fact that overwriting the local variables is the default behaviour doesn’t make it any better. I suggest deprecating it in PHP 7.3 and removing it in 8. In a whole Symfony-Stack (3.4) with all of it’s dependencies I could only find two usages of this function, both of which could be easily rewritten in vanilla PHP: https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Templating/PhpEngine.php#L148 https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Templating/PhpEngine.php#L158 Only downside: A polyfill is probably impossible since you cannot mutate the local symbol table of the callee (as far as I’m aware). Any thoughts? Regards