PHP用一个字符串调用多个方法

Question

I have the following string:

$str = "methodA()->methodB()->methodC"

And i want to call that "chain" on an object

$obj->$str

I am currently splitting with ()-> and calling one by one, but there must be abetter way.

How can i call it on one line? thanks!

EDIT: Some more context information:

I created a Doctrine Behaviour for symfony 1.4 to be able to make certain tables from the schema searchable with Zend Lucene.

In short, i need a way to say to the behaviour "To get the searchable field you must call methodA()->methodB()->methodC()"

EDIT2: Maybe i wasnt clear enough. $obj and $str are determined at runtime, so some of your suggestions are not applicable.

EDIT3: In case you are wondering, i am currently doing this:

  <?php
  $chain = explode("()->",$str);
  $method = array_shift($chain);
  $value = $obj->$method();
  foreach($chain as $method){
    $value = $value->$method();
  }

Answer 1

After writing my comment to the main question I thought of a possible solution, though a little verbose and manual (you would have to make as many case statements as you would reasonably expect for the number of chained methods).

function chain_execute($obj, $str) {
    $chain = explode("->",$str);
    $chain = array_map('trim', $chain);
    $chain_count = count($chain);
    switch($chain_count) {
        case 1:
            return $obj->{$chain[0]}();
            break;
        case 2:
            return $obj->{$chain[0]}()->{$chain[0]}();
            break;
        case 3:
            return $obj->{$chain[0]}()->{$chain[1]}()->{$chain[2]}();
            break;
        // etc.
        default:
            // not a value you were expecting
            throw new Exception('Invalid number of methods chained: ' . $chain_count);
            break;
    }
}

Usage would be:

$result = chain_execute($obj, "methodA->methodB->methodC");