<?php

class TestC {
  private $test;

  public function __construct( $val ) {
    $this->test = $val;
  }

  public function setVal( $val ) {
    $this->test = $val;
  }

  public function getVal() {
    return $this->test;
  }
}

function change_val( $class ) {
  $class->setVal( 'testing from function' );
}

$obj = new TestC('testing from construct');

call_user_func( 'change_val', $obj );

echo $obj->getVal();
// returns "testing from function"

?>