php中数组首字符过滤功能代码

<?php 
$array = array( 
'abcd', 
'abcde', 
'bcde', 
'cdef', 
'defg', 
'defgh' 
); 
$str = '~'.implode('~',$array).'~'; 
$word = $_GET['word']; //url = xxx.php?word=a 
preg_match_all("/~({$word}(?:[^~]*))/i",$str,$matches); 
var_dump($matches[1]); 

//