Group a flat associative array by elements with a certain key prefix and accumulate preceding elements into the parent group

I need to convert an associative array to a 2 dimensional array. The original array is as follows.

$data = [
    "data" => "data",
    "id_1553539135251" => "<p>nsmn</p>",
    "about" => "about",
    "id_1553539141598" => "<p>uiu</p>",
]

My code:

$data = $request->all();
$json = array();
foreach ($data as $key => $value) {
    if (strpos($key, 'id') !== false) {
        $json[$key]['content'] = $value;
    }
}

I need the following output.

[
    "id_1553539135251" => ["content" => "<p>nsmn</p>", "data" => "data"],
    "id_1553539141598" => ["content" => "<p>uiu</p>", "about" => "about"]
]

but my code outputs

[
    "id_1553539135251" => ["content" => "<p>nsmn</p>"],
    "id_1553539138029" => ["content" => "<p>jjkjk</p>"],
    "id_1553539141598" => ["content" => "<p>uiu</p>"],
]

$test = array(
    array(
        "data" => "data",
        "id_1553539135251" => "<p>nsmn</p>",
        "about" => "about",
        "id_1553539141598" => "<p>uiu</p>"
    ),
);

$output = array();
foreach ($test as $item) {
    $i = 0;
    $tt = '';
    foreach ($item as $k => $v) {
        if (strpos($k, 'id') !== false) {
            $output[$k] = array(
                'content' => $item[$k],
                'header' => $tt,
            );
        } else {
            $tt = $v;   
        }
    }
}
print_r($output);