<?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]);

//输出
//array(2) { [0]=> string(4) "abcd" [1]=> string(5) "abcde" }
//End_php