Merge two indexed arrays of associative arrays and group by column value to create an associative array of indexed arrays

Question

I have two 2d arrays and I want to merge them and group their data by a column value.

[
    ["year" => 2015, "value" => 32],
    ["year" => 2016, "value" => 54],
]

and

[
    ["year" => 2015, "value" => 300],
    ["year" => 2016, "value" => 5400]
]

Desired result:

Array(
    [2015]=>array(
        [0] => 32
        [1] => 95
    )
    [2016]=>array(
        [0] => 54
        [1] => 2068
    )
)

Answer 1

 $a = array(
     0 => array
         (
            "year" => 2015,
            "value" => 32
         ),
     1 => array
         (
            "year" => 2016,
            "value" => 54
         )  
 );

 $b = array(
     0 => array
        (
           "year" => 2015,
           "value" => 300
        ),
    1 => array
       (
           "year" => 2016,
           "value" => 5400
       )  
);

$c = array_merge($a,$b);

$output = array();
foreach($c as $key=>$val)
{
    $output[$val['year']][] = $val['value'];
}

echo '<pre>';
print_r($output);
exit;

Try this code..