怎样根据$hello数据将$str层层展开？解决方案

<?php

    $my_arr=array();

    $str="DIR_FS_AAA . DIR_WS_CLASSES";
    $hello=array(
        "DIR_FS_AAA"     =>"DIR_WS_TEMPLATE.'includes/'",
        "DIR_WS_CLASSES"    =>"DIR_WS_ADMIN.'helloworld'",
        "DIR_WS_TEMPLATE"    =>"template/",
        "DIR_WS_ADMIN"        =>"admin/"
    );

//怎样得到这样的结果数组：

     $my_arr=array(
         "DIR_FS_AAA . DIR_WS_CLASSES",
         "DIR_WS_TEMPLATE.'includes/'.DIR_WS_TEMPLATE.'includes/'",
         "template/includes/admin/includes/"
     );

?>

$my_arr[]    = $str;
$tmp    = preg_replace("/[A-Z_]+/e", "\$hello['\\0']", $str);
$my_arr[]    = $tmp;
$tmp    = preg_replace("/[\"']?\s*\.?\s*([A-Z_]+)\s*\.?\s*[\"']/e", "\$hello['\\1']", $tmp);
$my_arr[]    = $tmp;

//test
print_r($my_arr);
/**

Array
(
    [0] => DIR_FS_AAA . DIR_WS_CLASSES
    [1] => DIR_WS_TEMPLATE.'includes/' . DIR_WS_ADMIN.'helloworld'
    [2] => template/includes/admin/helloworld'
)

/**/