Illegal string offset foreach - php

Question

i have this code, and i get the error when i use foreach on the bottom of the page.
<table>
<tr>
<?php
$data =('https://www.example.com/api/report_advertiser?key=abcd&campaigns=6757955,6781745,6739793,6349821&quick=last_month');
$data_json = json_encode($data);
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $data);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$data_json);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
foreach ($response as $value)
echo $value['campaigns']
?>
</tr>
</table>

Answer 1

$response = curl_exec($ch);
Looking at this code, you should know that curl_exec() returns a string, when the execution was successful, otherwise false.
But in the next step you iterate over a string
foreach ($response as $value) {
echo $value['campaigns'];
}
You can iterate only over iterable types like arrays.
As it looks like you expect a JSON string you can convert it into an array. Use json_decode() for that and pass true as second parameter to receive an associative array instead of an object.
Assuming you will receive a multidimensional array having the inner loops key campaigns, following code will do the job.
$response = json_decode($response, true);
foreach ($response as $value) {
echo $value['campaigns'];
}
Update 1
Using the URL you provided before (I anonymized because you submitted credentials) you will receive an error.
if (!empty($response['errors'])) {
throw new Exception(print_r($response['errors'], true));
}
Gives out following, so it can not work as you expect, because the data is simply not available.
[status] => 405
[code] => 13
[title] => Method not allowed for this action