How to simulate the SQL LEFT JOIN operation using PHP arrays?

Question

I have an application that connects to multiple server. where one server will have ID that are foreign key to a table that is located on a different server. The issue here is that MySQL does not support linked servers so I can't run a left query that will LEFT join 2 tables located on separate servers.

So I have to pull 2 separate queries from 2 different server using PHP and they LEFT JOINing them using PHP.

Please note that the array keys listed below needs to be dynamic. I can't use a fixed names are different queries will have different column name. The example below use the phone_call_id as they key to use to join both arrays and it combines the column name. if $right_array has more columns then these columns need to be added to the final array.

so I have 2 array

$left_array = 
Array
(
    [0] => Array
        (
            [id] => 1
            [start_on] => 2014-09-14 19:50:00
            [end_on] => 2014-09-14 19:51:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 122
        )

    [1] => Array
        (
            [id] => 2
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 123
        )

    [2] => Array
        (
            [id] => 3
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 
        )
)

The right array will look like this

$right_array = 
Array
(
    [0] => Array
        (
            [account_id] => 1
            [phone_call_id] => 122
        )

    [1] => Array
        (
            [account_id] => 2
            [phone_call_id] => 123
        )
)

the results needs to be like this array

$joined_array = 
Array
(
    [0] => Array
        (
            [id] => 1
            [start_on] => 2014-09-14 19:50:00
            [end_on] => 2014-09-14 19:51:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 122
            [account_id] => 1
        )

    [1] => Array
        (
            [id] => 2
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 123
            [account_id] => 2
        )

    [2] => Array
        (
            [id] => 3
            [start_on] => 2014-09-15 05:53:00
            [end_on] => 2014-09-15 06:53:00
            [subject] => This is a new event
            [client_id] => 
            [all_day_event] => 0
            [event_type] => Event
            [phone_call_id] => 
            [account_id] =>

        )
)

Answer 1

This function simulates the left join operation

   //function to simulate the left join
    function left_join_array($left, $right, $left_join_on, $right_join_on = NULL){
        $final= array();

        if(empty($right_join_on))
            $right_join_on = $left_join_on;

        foreach($left AS $k => $v){
            $final[$k] = $v;
            foreach($right AS $kk => $vv){
                if($v[$left_join_on] == $vv[$right_join_on]){
                    foreach($vv AS $key => $val)
                        $final[$k][$key] = $val; 
                } else {
                    foreach($vv AS $key => $val)
                        $final[$k][$key] = NULL;            
                }
            }
        }
       return $final;
    }

//the function can be used like so assuming the column name in the left array is the same name as the right array

$final_array = left_join_array($left, $right, 'phone_call_id');

//the function can be used like so assuming the column name in the left array "are different but has the same corresponding value"

$final_array = left_join_array($left, $right, 'phone_call_id', 'p_c_id');