PHP如何修改文件中的某个变量内容????

譬如,有一个文件 var.static.php

============================
[PHP]
<?
/***********************
file var.static.php
***********/

$var1 = "Me";
$var2 = "He";
$var3 = "They";

?>
[/PHP]
=============================


那么,如何通过 change.php 来仅仅修改 var.static.php 中的变量 $var2,使

$var2 = "She"; ??????? ???????



(也就是如何直接修改 var.static.php ,使其内容变成:
============================
[PHP]
<?
$var1 = "Me";
$var2 = "She";
$var3 = "They";
?>
[/PHP]
=============================

)

谢谢 !!

dfsdf