Why does this JSON array appear empty? - php

Question

I am using a webservice to synchronize products from our distributor. As a first step, I have built a table to display the data to verify that everything is working properly. I have been able to successfully retrieve product descriptions using the following function:
function get_description($api_key, $item){
$url = 'http://www.stl-distribution.com/webservices/json/GetProductDescription.php';
$post_vars = 'api_key='.$api_key.'&item='.$item;
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST,1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$post_vars);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION,1);
curl_setopt($ch, CURLOPT_HEADER,0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
$return_data = curl_exec($ch);
$json_array = json_decode($return_data,true);
return $json_array;
}
I am displaying the information using a foreach loop as follows:
<table>
<tr>
<th>ISBN</th>
<th>Description:</th>
<th>Categories:</th>
<th>Options:</th>
</tr>
<?php foreach($product_ISBNs as $item) : ?>
<tr>
<td class="center"><?php echo $item[0]?></td>
<td class="center"><?php $item_description = get_description($api_key,$item[0]); echo $item_description['description'];?>
<td class="center"><?php $item_data = get_meta_data($api_key,$item[0]); echo $item_data['product_type']; ?>
</tr>
<?php endforeach?>
</table>
While I have successfully been able to retrieve the description using the get_description() function, I consistently get the following error from the get_meta_data() function:
Notice: Undefined index: product_type in C:\xampp\htdocs\STLImport\view\user_form.php on line 21
The code for the get_meta_data() function is as followss:
function get_meta_data($api_key, $item){
$url = 'http://www.stl-distribution.com/webservices/json/GetProductMetaBasic.php';
$post_vars = 'api_key='.$api_key.'&item='.$item;
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST,1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$post_vars);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION,1);
curl_setopt($ch, CURLOPT_HEADER,0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
$return_data = curl_exec($ch);
$json_array = json_decode($return_data,true);
return $json_array;
}
When I do a print_r() immediately before the return $json_array; statement I get the following error:
Array ( [0] => Array ( [error] => "" not found ) )
According to our distributor's website, our requests are being sent and received. Every time I refresh the page my usage stats go up. So, it appears that either no data is being returned, or I am not referencing it correctly. I know that these products exist in the database because it is returning the description. Therefore, I must not be referencing it correctly but I can't find where my error is. I have tried referencing it using various combinations to no avail. The webservice documentation gives this example for how the data should be returned:
{
"9781434768513":
{
"isbn13":"9781434768513",
"isbn":"1434768511",
"upc":"000000912992",
"title":"Crazy Love",
"subtitle":"Overwhelmed By A Relentless God",
"contributor1":"Chan, Francis",
"contributor2":"Yankoski, Danae",
"contributor3":"",
"vendor":"David C. Cook",
"release_date":"20080430",
"retail":"14.99",
"binding":"Paperback",
"product_type":"Books",
"category1":"Christian Living",
"category2":"",
"category3":"",
"grade_level_start":"",
"grade_level_end":"",
"inventory_updated":"20100825 11:25",
"tn_available":993,
"tn_onorder":240,
"nv_available":735,
"nv_onorder":0,
"image_small":"http:\/\/www.stl-distribution.com\/covers\/7814\/sm-9781434768513.jpg",
"image_medium":"http:\/\/www.stl-distribution.com\/covers\/7814\/md-9781434768513.jpg",
"image_large":"http:\/\/www.stl-distribution.com\/covers\/7814\/lg-9781434768513.jpg"
}

Answer 1

It seems that my get_meta_data() function had an error in it. My API provider informed me that this line
$post_vars = 'api_key='.$api_key.'&item='.$item;
Should have been
$post_vars = 'api_key='.$api_key.'&items='.$item;
Notice the addition of an 's'. So, $json_array appeared empty because it was empty. My other function worked because it did not require the 's' as GetProductMetaBasic did.
In addition, this line
<td class="center"><?php $item_data = get_meta_data($api_key,$item[0]); echo $item_data['product_type']; ?>
Should have been
<td class="center"><?php $item_data = get_meta_data($api_key,$item[0]); echo $item_data[$item[0]]['product_type']; ?></td>
because, as the sample data implied, the array was multidimensional. The desired value (product_type) was contained within the $item[0] array. Therefore, $item_data['product_type'] did not exist.