PHP 5.3 and Closures
I'm fairly excited because as of only a week or so ago I found the closures rfc, and not only did I find that the rfc has a working patch, apparently it's already in PHP 5.3.
You see, apparently it's not good enough that we get name spaces and late static binding, oh no, we get closures too!
I downloaded the Win32 snapshot from PHP snapshots page and indeed, closure support was included.
<?php $closure = function ($args) use ($global) { /*Body*/ }; ?>
According to the rfc, one must manually define external variables used within a function, however in my own tests you can still use the global keyword. The difference between the two is the use statement preserves the value of $global at creation and the global keyword would work as you would expect it to with a normal function. For example:
<?php $global = "Global Variable"; $closureUse = function ($arg) use ($global) { echo $global . " - " . $arg; }; $closureGlobal = function ($arg) { global $global; echo $global . " - " . $arg; }; echo "Basic Closure Tests\n"; echo "-------------------\n\n"; echo "\$closureUse('test'): "; $closureUse('test'); echo "\n"; echo "\$closureGlobal('test'): "; $closureGlobal('test'); echo "\n"; echo "\n"; echo "Global Closure Tests\n"; echo "--------------------\n\n"; $global = "Global Variable (Changed)"; echo "\$closureUse('test') (changed \$global): "; $closureUse('test'); echo "\n"; echo "\$closureGlobal('test') (changed \$global): "; $closureGlobal('test'); echo "\n"; ?>
Would output:
Basic Closure Tests
-------------------
$closureUse('test'): Global Variable - test
$closureGlobal('test'): Global Variable - test
Global Closure Tests
--------------------
$closureUse('test') (changed $global): Global Variable - test
$closureGlobal('test') (changed $global): Global Variable (Changed) - test
You can, as well, return references with a closure by putting the & between the function keyword and the parenthesis.
<?php $closureReturnsReference = function & ($args) use ($global) { /*Body*/ }; ?>
Just one of many shiny fancy things to look forward to in PHP 5.3.
Edit 7/23/2008:
I should mention to the people that trashed my examples on reddit, I'm sorry for assuming you knew what closures were and the the real world uses of them. I will try to refrain from giving a concise example of how a new language feature interacts with existing features and conventions, especially in PHP where things are a bit disorganized.
