Yesterday while documenting that PHP 6 deprecates $string{42} in favor of $string[42] I stumbled upon a comment within the PHP Manual XML sources, and here it is in its entirety:
<!-- maybe it's better to leave this out??
// this works, but i disencourage its use, since this is NOT
// involving functions, rather than mere variables, arrays and objects.
$beer = 'Heineken';
echo "I'd like to have another {${ strrev('reeb') }}, hips";
-->
The thought of a function being called from within a string (without eval()) seems a little odd, doesn’t it? Well, the above code in fact works. Not sure how useful it is but likely someone will find a creative use or two. The internals team generally feels that the behavior isn’t worth documenting as it’s simply an ugly and poor coding style BUT, maybe you’ll see it (the “{${ func() }}” syntax) on a PHP exam somewhere so now you know… :-)
History: This information was added within a patch titled “Added jeroen’s updates” by Damien Seguy apparently for Jeroen van Wolffelaar on the date Thu May 10 18:01:04 2001 UTC.
Update (April 20, 2007): A few days ago Jani demonstrated a simpler example for these variable functions:
$exec = ‘shell_exec’;
$cmd = ‘ls -l’;
echo “This is embedded exec: {$exec($cmd)}”;
It gets way better:
$a = array(1, 2, 3, 4, 4 => ‘beer’);
echo “I want {$a[“{$a[“{$a[“{$a[“{$a[0]}”]}”]}”]}”]}!\n”
Never have I been se grateful that a feature was _not_ published. You can only imagine what “uses” the folks over at strrev(‘bbphp’) would have found for this “feature”
Oh my god O_O
This is actually a fairly good feature. It’s called variable variables (http://www.php.net/manual/en/language.variables.variable.php). So the feature is actually quite documented and there is valid usage for this.
I think you are missing the point. I, for one, had no idea that you could call functions directly from a string.
$ab = ‘6’;
echo “ab: {${exit}}”;
Just another way to call eval(), I guess. And actually that’s exactly what it is:
echo “ab: {${;}}”;
Parse error: parse error, unexpected ‘;’ in xx : *eval()’d code* on line x;