PHP Using two class with the same name (Duplicate class name)

$v15_txt=file_get_contents($old_dir.'/libraries/joomla/version.php');
    $v15_txt=preg_replace('/class JVersion/i', 'class JVersion15', $v15_txt);
    eval('?>'.$v15_txt);
    $jvold=new JVersion15;
    $old_version = $jvold->RELEASE.'.'.$jvold->DEV_LEVEL;

    $v25_txt=file_get_contents($new_dir.'/libraries/cms/version/version.php');
    $v25_txt=preg_replace('/class JVersion/i', 'class JVersion25', $v25_txt);
    eval('?>'.$v25_txt);
    $jvnew=new JVersion25;
    $new_version = $jvnew->RELEASE.'.'.$jvnew->DEV_LEVEL;