php中计算二维数组中某一元素之和

[0] => array(5) {
["id"] => string(2) "11"
["name"] => string(5) "1.jpg"
["suffix"] => string(3) "jpg"
["url"] => string(29) "./Uploads/1/5292f55d208e8.jpg"
["size"] => string(6) "715895"
}
[1] => array(5) {
["id"] => string(2) "12"
["name"] => string(22) "minisite数据库.docx"
["suffix"] => string(4) "docx"
["url"] => string(30) "./Uploads/1/5292f5606a52c.docx"
["size"] => string(5) "16667"
}