get specific key value from array php

1$cnt = count(array_filter($array,function($element) {
2  return $element['your_key']=='foo';
3}));

1$ids = array_column($users, 'id');
2

1$people = array(
2  2 => array(
3    'name' => 'John',
4    'fav_color' => 'green'
5  ),
6  5=> array(
7    'name' => 'Samuel',
8    'fav_color' => 'blue'
9  ));
10$found_key = array_search('blue', array_column($people, 'fav_color'));

1$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');
2
3$key = array_search('green', $array); // $key = 2;
4$key = array_search('red', $array);   // $key = 1;
5

1    function cmp($a, $b)
2    {
3        return strcmp($a->display_name, $b->display_name);
4    }
5
6    usort($blogusers, "cmp");
7
8    foreach ($blogusers as $bloguser)
9    {
10        ...