PHP cURL - Strange problem with curl_setopt - php

Question

I have a very strange problem, here is my code :
function myFunction($id, $name, $secret) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://www.myurl.com/api');
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
http_build_query(
array(
'Client_id' => $id,
'Client_secret' => $secret, // $secret = Ve6UZ0cox=ry?2F9>qegmB:NCh?EQS?]cKmkjeHjS=3t1=E<RJ
'Client_name' => $name
)));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$results = curl_exec($ch);
$results = json_decode($results, true);
print_r($results);
curl_close ($ch);
// curl_close($curl);
return $results['Token_type'].' '.$results['Access_token'];
}
The code above doesn't work, probably due to special chars in $secret.
But, when I directly write the $secret value, it works!
curl_setopt($ch, CURLOPT_POSTFIELDS,
http_build_query(
array(
'Client_id' => $id,
// Now, it works!
'Client_secret' => 'Ve6UZ0cox=ry?2F9>qegmB:NCh?EQS?]cKmkjeHjS=3t1=E<RJ'
'Client_name' => $name
)));
Conclusion:
'Client_secret' => $secret // Doesn't work
'Client_secret' => 'Ve6UZ0cox=ry?2F9>qegmB:NCh?EQS?]cKmkjeHjS=3t1=E<RJ' // Work!
And yes, I tried this: die($secret);, which displays Ve6UZ0cox=ry?2F9>qegmB:NCh?EQS?]cKmkjeHjS=3t1=E<RJ as well.
What can you do please? Thank you for helping. ;-)
Cheers,
Seb