Using form method="post" to assign a php variable dynamically - php

Question

I'm trying to run a specific database query based on what value is selected in a select drop down. The current code I have isn't running the queries.
My current code looks like this:
main-search.php
<form action="" method="post">
<div class="search-container">
<input type="text" id="search_input" placeholder="">
<select name="search-by">
<option value="symptom">Symptom</option>
<option value="language">Language</option>
</select>
</div>
</form>
<?php
session_start();
$searchBy = $_POST['search-by'];
$_SESSION['search_type'] = $searchBy;
?>
search.php
<?php
session_start();
$queryType = $_SESSION['search_type'];
if ($queryType == "symptom") {
$searchQuery = $db->query("SELECT * FROM Symptoms WHERE symptom_name ORDER BY symptom_name ASC");
}
else if ($queryType == "language") {
$searchQuery = $db->query("SELECT * FROM `Language` WHERE language_name ORDER BY language_name ASC");
}
?>
I have tried changing the code in main-search.php to...
<?php
session_start();
$searchBy = $_POST['search-by'];
$_SESSION['search_type'] = "symptom";
?>
and it works as intended, running the first query, so that's why I'm assuming I'm doing something wrong with the post form and assigning the $searchBy value.
I'm new to php, so any help would be appreciated, thanks.

Answer 1

It's probably best to avoid Session variables for this purpose, as session variables are used to store/pass information from page to page in PHP (such as login status).
From my deduction you are trying to change this PHP variable dynamically when the user changes the <select> option. As PHP is a server-side script this will not work, if you need something to change without reloading the page you will need to use a client-side script (e.g. Javascript/jQuery). For example (in jQuery):
$('select[id="search-type"]').on("change", function(){
//Do work
});
However, if I understand you correctly, your best bet is to just use HTTP POST variables (accessed by $_POST in PHP), for example:
main-search.php:
<form action="search.php" method="post">
<div class="search-container">
<input type="text" id="search_input" placeholder="">
<select name="search_type" id="search-type">
<option value="symptom">Symptom</option>
<option value="language">Language</option>
</select>
<button type="submit">Submit</button>
</div>
</form>
search.php:
<?php
$queryType = $_POST['search_type'];
if ($queryType == "symptom") {
$searchQuery = $db->query("SELECT * FROM Symptoms WHERE symptom_name ORDER BY symptom_name ASC");
}
else if ($queryType == "language") {
$searchQuery = $db->query("SELECT * FROM `Language` WHERE language_name ORDER BY language_name ASC");
}
?>