function wp_send_json( $response ) {
 	2153	    @header( 'Content-Type: application/json; charset=' . get_option( 'blog_charset' ) );
 	2154	    echo json_encode( $json );
 	2155	    if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
 	2156	        wp_die();
 	2157	    else
 	2158	        die;
 	2159	}

$example = array(
	 'A' => array(
	 	 'A-1'
		,'A-2'
		,'A-3'
		,'A-4'
	 )
	,'B' => array(
		 'B-1'
		,'B-2'
	 )
);

function get_key( $value, $array, $parent_key = NULL )
{
	foreach ( $array as $k => $v )
	{
		if ( $v === $value )
		{
			return NULL === $parent_key ? $k : $parent_key;
		}
		if ( is_array( $v ) and $test = get_key( $value, $v, $k ) )
		{
			return $test;
		}
	}

	return FALSE;
}

print get_key( 'B-2', $example );

	do_action('retreive_password', $user_login);  // Misspelled and deprecated
	do_action('retrieve_password', $user_login);