Question

In terms of my data structure, I have an array of communications, with each communications_id itself containing three pieces of information: id, score, and content.

I want to implode this array in order to get a comma separated list of ids, how do I do this?

Answer 1

Update for PHP 5.5

PHP 5.5 introduces array_column which is a convenient shortcut to a whole class of array_map usage; it is also applicable here.

$ids = array_column($communications, 'id');
$output = implode(',', $ids);

Original answer

You need to make an array of just ids out of your array of communications. Then the implode would be trivial.

Hint: the function for that is array_map.

Solution:

Assumes PHP 5.3, otherwise you ‘d have to write the callback as a string.

$ids = array_map(function($item) { return $item['id']; }, $communications);
$output = implode(',', $ids);