variable class name

what's the correct syntax for: $a = new $b.'_helper'()?

[idev]

Guys, I need your help.

Looks simple, but can't figure out the best way to do that other than having a temporary variable.

This is the sample code that works:

<?php
class A_test {
  function b() {
    echo 'it worked';
  }
}
$a = new A_test();
$a->b();

This is the same with dynamic helper name, that I want to achieve:

<?php
class A_test {
  function b() {
    echo 'it worked';
  }
}
$mode = 'A';
$a = new $mode.'_test'();
$a->b();

any way to make the parser understand what I want?

P.S. new ${$mode.'_test'}() didn't work.

[eeek]

$a = new $mode.'_test'();

Try this:

$a=new A_test;

[idev]

Thanks for the attention, eeek, but please read the original request completely before you respond.

I still could find no way of doing that, so I went with a temporary variable:

$tmp = $mode.'_test';
$a = new $tmp();

I bet there's no other way w/ php5