Passing value from HTML form to php variable - php

Question

I'm trying to pass a value from an HTML form and store it to a php variable so i can use this variable into a query to determine what row to get from database. I'm using _post['category'] to get the selected value and I'm passing the variable to the query to get the desired row but I'm not getting anything so far any help will be appreciated. Here is what I wrote so far:
<form method="post" action="a34.php">
<select name="category">
<option value="6008">15</option>
<option value="6018">25</option>
<option value="6034">30</option>
<option value="6038">40</option>
$V=$_POST['category'];
$getrow= "SELECT ProdID,
ProdCatID, ID_AC_seperate, ProdImage,
ProdName, ProdPrice, ProdShippingPrice,
ProdShortDesc, ProdMediumDesc, suitable,
cart_thumb FROM accessories WHERE ProdID = '$V'";

Answer 1

I recommend you to use strip_tags function. Never put raw data into sql.
So
If(isset($_POST['category']) {
$data = strip_tags ($_POST['category']);
$getrow= "SELECT ProdID, ProdCatID, ID_AC_seperate, ProdImage,
ProdName, ProdPrice, ProdShippingPrice,
ProdShortDesc, ProdMediumDesc, suitable, cart_thumb
FROM accessories
WHERE ProdID = '. $data .'";
}

Answer 2

Okay, try the following.
The JS file detects when the user clicks an option and sends out an ajax request to the updateRow.php file with the $_POST variable of val.
updateRow.php takes the $_POST variable and casts it into an integer. The query is then updated with that variable. Process the query, then echo, print, etc. the data in the desired HTML format. Otherwise, the data echo 'failure'.
The output that is echoed, printed, etc is then sent back to the JS file under the variable data. If the data equals 'failure', then an error message is outputted. Otherwise, it inserts the HTML in the #row element.
// ------ Your JS file ---------
$(function() {
$row = $("#row");
$("#update-row").on("change", function() {
var val = $("select option:selected", this).val();
$.post('updateRow.php', {
val: val
}, function(data) {
if (data == 'failure') {
$row.text("Sorry, the row does not exist");
} else {
$row.html(data);
}
});
});
});
//------- updateRow.php ---------
//Make sure path/to/updateRow.php in the JS file is updated to here
$V = (int) $_POST['val'];
$getrow = "SELECT ProdID,
ProdCatID, ID_AC_seperate, ProdImage,
ProdName, ProdPrice, ProdShippingPrice,
ProdShortDesc, ProdMediumDesc, suitable,
cart_thumb FROM accessories WHERE ProdID =" . $V;
if ( QUERY_IS_SUCCESSFUL() ) {
echo 'The <b>HTML</b> you want to display the data in';
} else {
echo 'failure';
}
<!----- HTML file ---->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="path/to/js/file.js"></script>
<form method="post" action="a34.php" id="update-row">
<select name="category">
<option value="6008">15</option>
<option value="6018">25</option>
<option value="6034">30</option>
<option value="6038">40</option>
</select>
</form>
<div id="row"></div>