作为数据库查询的结果，我有以下对象，对象的最后一部分$result->meta_value是我感兴趣的。
我需要从字符串中获取这个值：
file";s:24:"2012/04/twitter.jpg";
谁能建议我如何将字符串分解成有用的东西？
object(stdClass)#72 (4) {
["meta_id"]=>
string(4) "2367"
["post_id"]=>
string(3) "540"
["meta_key"]=>
string(23) "_wp_attachment_metadata"
["meta_value"]=>
string(646) "a:6:{s:5:"width";s:3:"300";s:6:"height";s:3:"180";s:14:"hwstring_small";s:23:"height='76' width='128'";s:4:"file";s:24:"2012/04/twitter.jpg";s:5:"sizes";a:2:{s:9:"thumbnail";a:3:{s:4:"file";s:24:"twitterwinjs-150x150.jpg";s:5:"width";s:3:"150";s:6:"height";s:3:"150";}s:14:"post-thumbnail";a:3:{s:4:"file";s:22:"twitter60x60.jpg";s:5:"width";s:2:"60";s:6:"height";s:2:"60";}}s:10:"image_meta";a:10:{s:8:"aperture";s:1:"0";s:6:"credit";s:0:"";s:6:"camera";s:0:"";s:7:"caption";s:0:"";s:17:"created_timestamp";s:1:"0";s:9:"copyright";s:0:"";s:12:"focal_length";s:1:"0";s:3:"iso";s:1:"0";s:13:"shutter_speed";s:1:"0";s:5:"title";s:0:"";}}"
}