PHP: A string, two arrays and 4 loops result in a 0 - php

Question

In my android app user can upload up to 5 images for an item they have in their collection.
This is what my android app java code is sending over to the PHP server via POST:
[user_id=83,
item_id=24,
item_number_of_photos=1,
item_image_filename_0=http://www.asdqwe.net/item_images/83_image_2014-02-07-16-44-12.jpg,
item_image_description_0=mouse]
This is the PHP Code that handles it:
if (!empty($_POST)) {
$user_id = $_POST["user_id"];
$item_id = $_POST["item_id"];
$item_number_of_photos = $_POST['item_number_of_photos'];
for ($x=0; $x<$item_number_of_photos; $x++) {
if(isset($_POST['item_image_filename_'.$x]) && !empty($_POST['item_image_filename_'.$x])) {
$item_image_filenames[$x] = $_POST['item_image_filename_'.$x];
}
if(isset($_POST['item_image_description_'.$x]) && !empty($_POST['item_image_description_'.$x])) {
$item_image_descriptions[$x] = $_POST['item_image_description_'.$x];
}
}
$query_add_item_photos = "INSERT INTO
product_photos (
product_id,
product_photo,
product_photo_added_by_user,
product_photo_description
)";
////////////////////////////////////////////////////////////
////ADD THE PHOTOS TO THE PHOTOS TABLE//////////////////////
////////////////////////////////////////////////////////////
try {
for($x = 0; $x<$item_number_of_photos; $x++) {
$query_add_item_photos+= " VALUES
(
:product_id,
:product_photo_filename_" . $x .",
:product_photo_added_by_user,
:product_photo_description_" . $x . "
)";
}
$input_parameters = array(
':product_id' => $item_id,
':product_photo_added_by_user' => $user_id,
);
for($x = 0; $x<$item_number_of_photos; $x++) {
$input_parameters[':product_photo_filename_' . $x] = $item_image_filenames[$x];
$input_parameters[':product_photo_description_' . $x] = $item_image_descriptions[$x];
}
$sth = $connection->prepare($query_add_item_photos);
$sth->execute($input_parameters);
} catch(PDOException $pe) {
$response["success"] = $http_response_server_error;
$response["message"] = $http_response_server_error . $pe . $query_add_item_photos;
die(json_encode($response));
}
$response["success"] = $http_response_success;
$response["message"] = "WE MADE IT";
die(json_encode($response));
$connection = null;
} else {
$response["success"] = $http_response_bad_request;
$response["message"] = $http_message_bad_request;
die(json_encode($response));
$connection = null;
}
At the end when I run this, I get a PDO error saying that the query = "0".
I have only basic understanding of PHP so this is huge pain for me

Answer 1

Local Variables Issue
In your for loop, you are assigning values to $item_image_filenames[$x] array element and also to $item_image_descriptions[$x] array element.
for ($x=0; $x<$item_number_of_photos; $x++) {
...
$item_image_filenames[$x] = $_POST['item_image_filename_'.$x];
...
$item_image_descriptions[$x] = $_POST['item_image_description_'.$x];
}
But (assuming you have posted all of your code), these 2 arrays fall out of scope and disappear as soon as you exit your for loop. They weren't defined before your for loop, which means that they are being defined local to your for loop.
The result of this is that, later, when you attempt to reference these arrays, they don't exist, and they have no values. So, later on in your code...
for($x = 0; $x<$item_number_of_photos; $x++) {
$input_parameters[':product_photo_filename_' . $x] = $item_image_filenames[$x];
$input_parameters[':product_photo_description_' . $x] = $item_image_descriptions[$x];
}
... is going to result in assigning to $input_parameters values that don't exist.
To solve this problem, define $item_image_filenames and $item_image_descriptions before you enter your for loop. This way, they will continue to exist inside and after your for loop. You can do this:
$user_id = $_POST["user_id"];
$item_id = $_POST["item_id"];
$item_number_of_photos = $_POST['item_number_of_photos'];
// Define empty arrays so that I can use them throughout my code.
$item_image_filenames = array();
$item_image_descriptions = array();
for ($x=0; $x<$item_number_of_photos; $x++) {
...
String Concatenation Syntax
I also noticed that your line of code:
$query_add_item_photos+= " VALUES
...
... is not the correct way to do string concatenation in PHP. You want to use .= instead of +=. In PHP, strings are concatenated with ., as in the example: $string1 = $string2 . $string3;
Your code should instead be:
$query_add_item_photos .= " VALUES
...