Using global inside an eval()

[rolando]

Hola.

Is it just me, or is eval() just a giant pain in the tookus?...

Here's my issue. I'd really like to know if anyone knows something on this subject that I don't.

I'm using an XSLT/XML setup to produce PHP pages that are cached for later use. When I load the pages from cache (i.e. they are loaded direct to the browser via include()), everything is fine.

The admin for this system allows the administrator to preview any changes he's made before the result string is saved to the cache file. I do this by taking the result string (i.e. the string containing the new PHP page) and eval()'ing it. That looks like:

eval("?>" . $result);

The result string contains an include() statement that pulls in a piece of 3rd party code that uses a bunch of functions (to sum up: within the eval, a bunch of functions are declared.) These functions use global to pull in some variables that are also declared inside the eval() within it's top-level scope. I ran some tests, and these globaled vars don't make it into the function scope. Here's an example of what I mean:

FILE myfile.php:
<?php

$globalvar = "stuff";

function my_func() {
global $globalvar;

if (isset($globalvar)) {
echo "it's real";
} else {
echo "it's not real";
}
}

?>

FILE main.php:
<?php
$str = join("",file("myfile.php"));

eval("?>" . $str);
?>

According to my experience, the output of running main.php would be

it's not real

This would be imply that global cannot be used inside an eval()? Any experience to the contrary or to the agreement?

Thanks much, all!

-Roy

[rolando]

Hola.

Writing the post above made me realize the problem! Well, it could be an object lesson for anyone who reads this... 🙂

The problem was that anything declared inside the eval() is not a part of the global scope. eval() is a function, rather than a language construct. So anything declared in eval() is not global (even though it later persists in the global scope after the eval() is done.) The global construct only allows you to grab global vars. So, those vars can't be global'd.

eval() seems to be very problematic in this way. It's meant to work the way I tried to use it, but it doesn't. My $.02 for the community is that the Zend engine really needs a language construct that performs the effects of eval() and actually has the desired behavior.

Hope this helps y'all.

-Roy

[rolando]

Hmm... I have now thoroughly made a fool of myself in a public forum...

Okay, I am incorrect about eval() not placing new vars in the global scope. I was using eval() inside a function, and that was causing the scope problems.

Please ignore these 3 undeletable posts...

-Roy