Retrieve the next key in an array from given key

get-next-array-key.php

<?php

/**
 * Retrieve the next key in an array from given key.
 *
 * @since    1.0.0
 * @param    array   $arr        List of items in a form of array.
 * @param    integer $key        Key to search and find within the array.
 * @return   integer
 */
function prefix_get_next_key_array( $arr, $key ) {
	$keys     = array_keys( $arr );
	$position = array_search( $key, $keys, true );

	if ( isset( $keys[ $position + 1 ] ) ) {
		$next_key = $keys[ $position + 1 ];
	}

	return $next_key;
}