PHP merge two arrays on the same key AND value

Question

I have two arrays. And I want to merge them on the same key AND value. If they have the same ur_user_id then they are merged. array2 only provides

Answer 1

When you need to make iterated checks/searches for values (effectively a unique identifier), the best performing approach will often:

1. generate a keyed array and
2. make iterated calls of isset() (instead of in_array() or array_search())

ur_user_id is your "unique identifier".
$array2 is prepared by assigning ur_user_id values as keys with array_column().
$array1 controls the number of iterations.
My approach will check for a corresponding row between $array1 and $array2 (to avoid Notices) before using a union operator (+=) to append the $array2 data to each original row of $array1.
The & in the foreach loop "modifies by reference" -- this means the actual input array is being "dealt with" instead of a copy of the input array.

Code: (Demo)

$array1 =    
    array(
        array('ur_user_id'=> 1,'ur_fname'=>'PerA','ur_lname'=>'SonA'),
        array('ur_user_id'=> 2,'ur_fname'=>'PerB','ur_lname'=>'SonB'),
        array('ur_user_id'=> 3,'ur_fname'=>'PerC','ur_lname'=>'SonC'),
    );
$array2 = 
    array(
        array('ur_user_id' => 5,'ur_code' => 'EE','ur_user_role' => 'testE'),
        array('ur_user_id' => 4,'ur_code' => 'DD','ur_user_role' => 'testD'),
        array('ur_user_id' => 6,'ur_code' => 'FF','ur_user_role' => 'testF'),
        array('ur_user_id' => 3,'ur_code' => 'CC','ur_user_role' => 'testC'),
        array('ur_user_id' => 1,'ur_code' => 'AA','ur_user_role' => 'testA'),
        array('ur_user_id' => 2,'ur_code' => 'BB','ur_user_role' => 'testB'),
    );  

$keyed = array_column($array2, NULL, 'ur_user_id'); // replace indexes with ur_user_id values

foreach ($array1 as &$row) {       // write directly to $array1 while iterating
    if (isset($keyed[$row['ur_user_id']])) { // check if shared key exists
        $row += $keyed[$row['ur_user_id']]; // append associative elements
    }
}

var_export($array1);

Output:

array (
  0 => 
  array (
    'ur_user_id' => 1,
    'ur_fname' => 'PerA',
    'ur_lname' => 'SonA',
    'ur_code' => 'AA',
    'ur_user_role' => 'testA',
  ),
  1 => 
  array (
    'ur_user_id' => 2,
    'ur_fname' => 'PerB',
    'ur_lname' => 'SonB',
    'ur_code' => 'BB',
    'ur_user_role' => 'testB',
  ),
  2 => 
  array (
    'ur_user_id' => 3,
    'ur_fname' => 'PerC',
    'ur_lname' => 'SonC',
    'ur_code' => 'CC',
    'ur_user_role' => 'testC',
  ),
)