Error when Updating query using PDO - php

Question

I have set a custom function to update my query however it doesn't seem to read the variables i am not sure where i am going wrong.
This is my function.
function update_product($productID, $productName, $productDescription, $productPrice, $categoryID){
global $conn;
$sql = "UPDATE product SET productName = :productName, productDescription = :productDescription, productPrice = :productPrice, categoryID = :categoryID WHERE productID = :productID";
$statement = $conn->prepare($sql);
$statement->bindValue(':productName', $productName);
$statement->bindValue(':productDescription', $productDescription);
$statement->bindValue(':productPrice', $productPrice);
$statement->bindValue(':categoryID', $categoryID);
$statement->bindValue(':productID', $productID);
$result = $statement->execute();
$statement->closeCursor();
return $result;
}
This is where i am calling the function
$result = update_product($productID, $productName, $productDescription, $productPrice, $categoryID);
I will also add my function where i am getting the ID and loading the inputs...
function select_productspreparedGETID(){
global $conn;
$productID = $_GET['id'];
//prepared
$sql = "SELECT * FROM product WHERE productID = :productID";
$statement = $conn->prepare($sql);
$statement->bindValue(':productID', $productID);
$statement->execute();
$result = $statement->fetchAll();
$statement->closeCursor();
foreach($result as $row):
?>
<form method="post" action="../controller/product_update_process.php" enctype="multipart/form-data">
<div>
<label>Name* </label>
<input id="Product_Name" type="text" name="Product_Name" value="<?php echo $row['productName'] ?>" />
</div>
<div>
<label>Description* </label>
<textarea id="productDescription" name="productDescription" /><?php echo $row['productDescription'] ?></textarea>
</div>
<div>
<label>Price* </label>
<input id="Price" type="text" name="Price" value="<?php echo $row['productPrice'] ?>" />
</div>
<input type="submit" name="submit" value= "Update Cart">
</form>
<?php
endforeach;
}
Any advice on how to improve my structure or better yet beat this error would be seriously appreciated i have been stuck for the last 20hours.

Answer 1

You are defining $productID = $_GET['id']; inside a function and using the same variable in another function. The $productID is clearly not available to other functions. Make sure that it is defined outside any functions.
Currently the variable is only available to the local scope in which it is defined. For example, define $productID outside any functions:
$productID = $_GET['id'];
You can send this variable to select_productspreparedGETID() as an argument:
function select_productspreparedGETID($productID){
//Your code
}
And then you have $productID inside both functions update_product() and select_productspreparedGETID() because update_product() already has $productID as an argument.