ClosureMaker enables the use of PHP 5.3-like closures in prior PHP versions.
A nice little tool for those of us who don't have the option to upgrade
to PHP 5.3 any time soon.
 
Usage:
=====
Below is an example code:
 
//Declare some variables
$a = 5;
$b = array('foo' => 'bar');
 
//Create the lambda function. Notice the following:
//   1) ClosureMaker uses a PHP 5.3 style of declaring the function
//   2) The magic $_ can be used inside your code to access variables
//      in the 'environment' of the closure
//   3) We pass get_defined_vars() to the closure. This gives us access to
//      a snapshot of the current set of declared variables inside the closure
$lambda = ClosureMaker::create(
 <<<PHP
 function (\$x, \$y) {
    if (\$x == \$y) {
        return \$x;
    }
    var_dump(\$_['b']);
    return \$_['a'];
}
PHP
, get_defined_vars());
 
//Here we redeclare $a and $b for good measure
$a = 4;
$b = null;
 
echo "\nTest1\n";
var_dump($lambda(3, 3));
echo "\nTest2\n";
var_dump($lambda(4, 1));
 
As expected, this outputs:
Test1
int(3)
 
Test2
array(1) {
 ["foo"]=>
 string(3) "bar"
}
int(5)
 
Notice how test two gives us back the values of $a and $b at the time the
closure was created.