PHP - Combine arrays with same key value

Question

I have a JSON array of multiple objects, here's an example:

$people = [{"name":"John", "color":"green"}, 
           {"name":"Mary", "color":"green"}, 
           {"name":"Bob", "color":"red"}]

I use json_decode($people, true) to convert them to an array...

Now let's say I want to combine those that have the same color. I'd have to do array_merge_recursive($people[0], $people[1]) because they both have green as the color. Note that I have to specify which ones I want to merge recursively.

How can I loop through $people after it's been decoded to an array format and automatically merge recursively those that have the same key value?

Something like this:

foreach($people as $person) {
    // If a person has same color of previous
    // person then merge them recursively.
}

So that I could get this after looping:

[{"name":"John, Mary", "color":"green, green"}, 
 {"name":"Bob", "color":"red"}]

Use an associative array whose key is the color.

Barmar
– Barmar

2014-11-07 16:48:50 +00:00
Commented Nov 7, 2014 at 16:48 — Barmar
– Barmar, Commented Nov 7, 2014 at 16:48

Barmar · Accepted Answer · 2014-11-07 17:04:25Z

2

Make the result array an associative array keyed by the color.

$people_by_color = array();
foreach ($people as $person) {
    if (isset($people_by_color[$person['color']])) {
        $people_by_color[$person['color']]['name'] .= ', ' . $person['name'];
        $people_by_color[$person['color']]['color'] .= ', ' . $person['color'];
    } else {
        $people_by_color[$person['color']] = $person;
    }
}
$people_by_color = array_values($people_by_color); // Turn into indexed array

edited Nov 7, 2014 at 17:04

answered Nov 7, 2014 at 16:52

Barmar

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1 Comment

jstudios Over a year ago

This worked perfectly, thanks! BTW, you missed a parenthesis on the if statement. I removed the color line after the name because I don't really want to combine two values that are the same, I just figured it would combine them regardless if using array_merge_recursively.

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