Nested object method calls from string

As long as they don't have any arguments, you COULD do this (Not that robust since it could be broken pretty easily by a malformed string. But you could add a lot more error checking and support for arguments if you really tried)...:

$methods = explode('->', $b);

$ref = &$a;
foreach ($methods as $method) {
    $method = preg_replace('#\\(.*?\\)#', '', $method);
    $ref = &$ref->$method();
}

But I agree with NullUserException that it's typically a sign of bad design... (I think chaining in general is a sign of bad design, but that's just my personal opinion)...

But either way, it's a lot safer than eval, so if you must, you may want to try something like this...

Edit: Based on your updated answer (wanting to map a function to an array of objects):

Using php 5.3:

$newArray = array_map(
    function($value) { 
        return $value->parent()->name;
    },
    $array
);

Or with PHP <= 5.2:

$func = create_function('$value', 'return $value->parent()->name;');
$newArray = array_map($func, $array);

So, your final map method becomes:

public function map($string) {
    $func = create_function('$value', 'return $value' . $string . ';');
    $return = array();
    foreach ($this as $key => $value) {
        $return[$key] = $func($value);
    }
}

Since it's not an array, array_map won't work directly... But you can iterate over the object itself.

But beware, this is no safer than eval, so you really should look at a different solution (such as mapping a callback):

public function map($callback) {
    $return = array();
    foreach ($this as $key => $value) {
        $return[$key] = $callback($value);
    }
}

Usage:

$array = $collection->map(function($value) { return $value->parent()->name; });

You might have to check into "eval":

eval('$a' . $b);

But beware: Unless you control $b yourself, you might be opening yourself up for bad things to happen. This can be a major security hole if $b comes from any source the user can change or leak changes to!

I'm trying to do sth like ruby map for my own collection object (build on arrayobject). If I have array of objects I wont to do sth like this:

$people->map('name') //which should return array of names

or

$people->map('parent()->name') //which should return array of names of parents