How can I create an array of variables based on an associative array's value in PHP?

Question

Given the following array

 ( 
 0 => array( 
     'orders_messaging_info_id' => '1',
     'column_name' => 'message_route',
     'column_info' => 'internal',
     ),
 
 1 => array(
     'orders_messaging_info_id' => '2',
     'column_name' => 'message_route',
     'column_info' => 'external',
     ),
 
 2 => array(
     'orders_messaging_info_id' => '3',
     'column_name' => 'message_type',
     'column_info' => 'SMS',
     ),
 
 3 => array(
     'orders_messaging_info_id' => '4',
     'column_name' => 'message_type',
     'column_info' => 'email',
     ),
 
 4 => array(
     'orders_messaging_info_id' => '5',
     'column_name' => 'message_type',
     'column_info' => 'slack',
     ),
 
 5 => array(
     'orders_messaging_info_id' => '6',
     'column_name' => 'message_type',
     'column_info' => 'plaintext',
     ),
 
 6 => array(
     'orders_messaging_info_id' => '10',
     'column_name' => 'message_text',
     'column_info' => 'JSON',
     ),
 )

how can I create three associative arrays named for the value of 'column_name' whose keys are the value at 'orders_messaging_info_id' and values are at 'column_info'?

I tried using extract() in a foreach loop on the value of 'column_name' to create three variables -- one for each distinct value -- but I don't know how to access the other two values per array to assign them. And once I tackle that, I know I'll have to figure out a way to add values to the arrays that extract() creates, such as with the array variable that will be named $message_type[] or $message_route[]

The expected array would look like

$message_route = array('1'=>'internal','2'=>'external');

Answer 1

While PHP makes it possible to generate "variable variables", it is typically considered poor practice to do so. Variable variables are effectively suboptimally structure arrays. You are still packagin array-like data, but in a manner that eliminates the opportunity to enjoy PHP's suite of array functions. It's like forcing yourself to type code with your keyboard super-glued to the underside of your desk -- there's no benefit.

This is a working solution, but it is:

• Not easy to read
• Likely to confuse your IDE because it will not be able to trace your subsequently accessed variables ( like message_text, etc.)
• Individual variables will need to be called by name instead of being accessible inside of a loop or function.
• You will need to check if each array exists because depending on the payload, some expected variables may not be declared.

Code: (Demo)

foreach ($array as $row) {
    ${$row['column_name']}[$row['orders_messaging_info_id']] = $row['column_info'];
}
 
var_export($message_text);
echo "\n---\n";
var_export($message_route);
echo "\n---\n";
var_export($message_type);

---

Instead, I recommend that you abandon the notion of using variable variables and use a single result array that has first-level keys with the same intended meaning. Calling extract() on each row will help to improve readability as well. (Demo)

$result = [] ;
foreach ($array as $row) {
    extract($row);
    $result[$column_name][$orders_messaging_info_id] = $column_info;
}
 
var_export($result);

Answer 2

extract() doesn't really help you here. Instead, you should make use of variable variables (https://www.php.net/manual/en/language.variables.variable.php). Something like:

<?php

$array = array(
 0 => array( 
     'orders_messaging_info_id' => '1',
     'column_name' => 'message_route',
     'column_info' => 'internal',
     ),
 1 => array(
     'orders_messaging_info_id' => '2',
     'column_name' => 'message_route',
     'column_info' => 'external',
     ),
 2 => array(
     'orders_messaging_info_id' => '3',
     'column_name' => 'message_type',
     'column_info' => 'SMS',
     ),
 3 => array(
     'orders_messaging_info_id' => '4',
     'column_name' => 'message_type',
     'column_info' => 'email',
     ),
 4 => array(
     'orders_messaging_info_id' => '5',
     'column_name' => 'message_type',
     'column_info' => 'slack',
     ),
 5 => array(
     'orders_messaging_info_id' => '6',
     'column_name' => 'message_type',
     'column_info' => 'plaintext',
     ),
 6 => array(
     'orders_messaging_info_id' => '10',
     'column_name' => 'message_text',
     'column_info' => 'JSON',
     ),
 );
 
 foreach($array as $entry) {
     $name = $entry['column_name'];
     if (!isset($$name)) {
        $$name = [];    
     }
     $$name[$entry['orders_messaging_info_id']] = $entry['column_info'];
 }
 
 var_dump($message_text, $message_route, $message_type);