Question

Note: I have condensed this article into my person wiki: http://wiki.chacha102.com/Lambda – Enjoy

I am having some troubles with Lambda style functions in PHP.

First, This Works:

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

Second, This Works:

class Bar{
    public function foo(){
       echo "Bar";
    }

Third, This works:

$foo = new stdClass;
$foo->bar = function(){ echo "bar"; };
$test = $foo->bar;
$test();

But, this does not work:

$foo = new stdClass;
$foo->bar = function(){ echo "bar"; };
$foo->bar();

And, this does not work

class Bar{
    public function foo(){
       echo "Bar";
    }
$foo = new Bar;
$foo->foo = function(){ echo "foo"; };
$foo->foo(); // echo's bar instead of Foo.

My Question is Why?, and how can I assure that both this:

$foo->bar = function(){ echo "test"; };
$foo->bar();

and this

$foo = new Bar;
$foo->bar();

are called properly? Extra Points if you can point to documentation stating why this problem occurs.

Answer 1

This is an interesting question. This works:

$a = new stdClass;
$a->foo = function() { echo "bar"; };
$b = $a->foo;
$b(); // echos bars

but as you say this doesn’t:

$a = new stdClass;
$a->foo = function() { echo "bar"; };
$a->foo();

If you want an object to which you can dynamically call members, try:

class A {
  public function __call($func, $args) {
    $f = $this->$func;
    if (is_callable($f)) {
      return call_user_func_array($f, $args);
    }
  }
}

$a = new A;
$a->foo = function() { echo "bar\n"; };
$a->foo2 = function($args) { print_r($args); };
$a->foo();
$a->foo2(array(1 => 2, 3 => 4));

But you can’t replace callable methods this way because __call() is only called for methods that either don’t exist or aren’t accessible (eg they’re private).