Generate the array like this.
$enquiries_labels = array("Key1" => "New Enquiry", "Key2" => "Retail Enquiry","Key3" => "Feedback", "Key4" => "Payment Query","Key5" => "Package Query", "Key6" => "Test Query");
Write down Key you want here.
$enquiries_labels = array("New Enquiry","Retail Enquiry","Feedback","Payment Query","Package Query","Test Query");
This array will generate key from 0 onward & you will get keys and values like this.
foreach ($enquiries_labels as $key => $value) {
echo $key;
echo $value;
}