php - Easiest way to implode() a two-dimensional array?

Question

I'm new to PHP, and don't have quite the grip on how it works. If I have a two dimensional array as such (returned by a database):

array(3) {   
    [0]=> array(1) {         
        ["tag_id"]=> string(1) "5" 
    } 
    [1]=> array(1) {         
        ["tag_id"]=> string(1) "3" 
    } 
    [2]=> array(1) {         
        ["tag_id"]=> string(1) "4" 
    } 
}

and want to turn it into the string 5,3,4 what would be the quickest way do do this? I currently have an obnoxious foreach loop, but was hoping it could be done in one line. A standard implode gives me Array,Array,Array.

Answer 1

This modifies your array using array_map, but probably for the better by turning it into a 1D array of tag_id's. Then you can just use implode like normal:

$arr = array_map(function($el){ return $el['tag_id']; }, $arr);
$str = implode(',', $arr);

If you don't want to modify your array than you can just do this:

$str = implode(',', array_map(function($el){ return $el['tag_id']; }, $arr));

Codepad Demo