Split Multi Dimensional array into single array :PHP

I have an array (From mysql),

Array ( 
    [0] => Array ( 
        [heading] => Page Name change 
        [name] => Page_Name_change 
        [menu] => online 
    ) 
    [1] => Array ( 
        [heading] => Lorem ipsum dolor 
        [name] => Lorem_ipsum_dolor_ 
        [menu] => akshaya 
    ) 
    [2] => Array ( 
        [heading] => fgdfgfdgdfgdf 
        [name] => fgdfgfdgdfgdf 
        [menu] => akshaya 
    ) 
)

I need to split it into separate arrays, basis on [menu], check this php

function getpage() {
    $query = "SELECT heading,name,menu FROM pages";
    $res = $this->_conn->query($query);
    while ($row = mysqli_fetch_assoc($res)) {
        $result[] = $row;
    }
    for ($i=0; $i < count($result); $i++) {
        if (strcmp($result[$i]['menu'],'akshaya') == 0) {
            for ($j=0; $j < count($result[$i]) ; $j++)
                $menu = $result[$i][$j];
        }
    }
    //if(strcmp($row['menu'],'akshaya')==0) { }
    return $menu;
}

The expected result is the array where each menu segment has the list of the elements from the initial array, like that:

[
    'online' => [
        [
            'heading' => '...',
            'name' => '...',
        ],
    ],
    'akshaya' => [
        [...], 
        [...],
    ],
]

its for display an Navigation Menu & Submenu,