Optimize a "crossing data" email-us form - php

Question

I recently had a job to optimize a client's website that contains an extremelly cumbersome form in a client's website. I want to optimize it, but I don't quite know where to start.
The website is a "service" database. This database has a special form that allows to send a email to all service providers of a specific type, depending on 2 filters: Location and Service Category. The purpose of this is to ask for a price for a job to several service providers (for example "I need a job in my house, my sink needs replacement, what is the price of that job, etc etc" and it would send an email to several "plumbers" in that location so they would answer and find the cheapest/best one).
So, we have several "if" conditions on a php script that have all combinations with a email list. Here is a snippet of the code:
<?php
if(($sendLocal == "cascais-oeiras") && ($sendCat == "canalizadores")){$mailToList = "email1#gmail.com, email2#gmail.com, email3#gmail.com, email4#gmail.com";}
else if(($sendLocal == "cascais-oeiras") && ($sendCat == "eletricistas")){$mailToList = "email1#gmail.com";}
else if(($sendLocal == "cascais-oeiras") && ($sendCat == "pintores")){$mailToList = "email1#gmail.com, email2#gmail.com, email3#gmail.com, email4#gmail.com, email5#gmail.com";}
...
?>
This extends for a several lines (about 480), because there are about 13 locations ($sendLocal) and 36 service categories ($sendCat). The emails are hardcoded in the script, and managing them is a huge hassle.
Now, I don't need a full script coded, I just want some guidance on where to start and what method to use. I need a way to cross 2 variables (in this case, location and type) and it would return me the ones that only exist in both.
Is there a better way to do this without using a 500 "if" line list? I have no problem coding it from scratch, or using another language/script altogheter.
Thank you.

Answer 1

I would define an array, and then get the addresses from the array. See the example below.
It would, of course, be even better if you would store the addresses in a database (sqlite, mysql, whatever), this way you don't need to edit a piece of code (which is error-prone & comparatively difficult) every time an address needs to be added/removed/changed.
<?php
$lists = [
'cascais-oeiras_canalizadores' => [
'address#example.com',
'moar#example.com',
],
'cascais-oeiras_eletricistas' => [
'address#example.com',
'moar#example.com',
],
# ... and so forth
];
# Note you don't *need* to have $lists hard-coded here, obviously, you could
# also get it from somwhere else, like, read it from a database or text file.
$key = "{$sendLocal}_{$sendCat}";
if (!isset($lists($key)) {
print('No such list');
exit(1);
}
$mailToList = implode(', ', $lists);