Description:
------------
With the intorduction of closures it would be nice to be able to have some control over native functions for example:


$foo = function() { 
echo 'bar';
}

$foo();

Works fine. 


It would be nice to be able to do something like

function foo() {
echo 'bar';
}

$foo = &foo;
$foo();

And ultimately, override the defined function:

function foo() {
echo 'bar';
}

$oldFoo = &foo;
foo = function() use ($oldFoo) {
   $oldFoo();
   echo 'bar';
}


foo(); // will print 'foobar';

There are several uses for this, just look at the way closures are commonly used in javascript. It's really useful for debugging, as a function can be substituted easily.

Though this probably isn't possible due to the clear distinction php makes between functions and variables.