Obtener la clave del elemento de matriz PHP
$people = array(
2 => array(
'name' => 'John',
'fav_color' => 'green'
),
5=> array(
'name' => 'Samuel',
'fav_color' => 'blue'
));
$found_key = array_search('blue', array_column($people, 'fav_color'));
Andrew Lautenbach