- array_keys: documentation ( source)
- current: documentation ( source)
<?php
$rates = array(
'flatrate_flatrate' => 4.5,
'matrixrate_matrixrate_1', 10,
'matrixrate_matrixrate_2', 15,
'matrixrate_matrixrate_3', 15,
'matrixrate_matrixrate_4', 20
);
echo current(array_keys($rates));