Replace PHP values in $_POST (for mailing) - php

Question

This is driving me crazy and I couldn't find information that could help me figure this out.
I have a simple check-in form as follows:
<label for="adults" class="field-label"> Adults</label>
<label class="field select prepend-icon">
<select id="adults" name="adults" onChange="updatesum()">
<option value="0">...</option>
<option value="300">1</option>
<option value="600">2</option>
<option value="900">3</option>
</select>
</label>
Those option values are prices used to calculate the price per person and the text is actually the amount of adults checkin-in.
What I can't figure out is that when I submit the form the PHP posts the value of the field instead of the amount of adults checking in which are between 1 and 3 max.
$adults = strip_tags(trim($_POST["adults"]));
Can i replace that values before sending the email to something like this:
If the value = 300 then replace with 1
If the value = 600 then replace with 2
If the value = 900 then replace with 3
and then send the email with the number of adults and not the price.
Can anybody give me a hand?? thanks!!
You can check it live here westermansfrigga.se and press the button "boka nu", that's the form I'm making.
It's still in testing phase you can make test bokings and you should get the corresponding emails. For a clear understanding of what I mean with replacing the values. In the confirmation email adults = 300 instead of 1.

Answer 1

The behaviour of your form is the expected one. The value of the field is sent, not its text. So
<option value="ThisWillBeSent">This will NOT be sent</option>
I imagine that you use "value" for some operation on onChange (so if I were you, I would add that script to the question). The best solution would be to have a different attribute holding the number:
<option data-value="300" value="1">One Adult</option>
This way, the number of adults gets sent, and the client still has the amount to work upon. In the javascript you read the new attribute, e.g. in jQuery,
sum += $el.attr("data-value")
instead of
sum += $el.attr("value")
If you're using plain Javascript, then you would have something like
var combo = document.getElementById("adults");
var adultValue = combo.options[combo.selectedIndex].getAttribute("data-value");
To replace values server side, in PHP, you can use switch:
switch ($valueIn) {
case 300: $valueOut = 1; break;
case 600: $valueOut = 2; break;
case 900: $valueOut = 3; break;
default:
// Throw some error, to be warned should you ever change
// the client side array and get an unknown value such as 1200.
}
(or, in this case, also $valueOut = $valueIn / 300).