cURL / JSON file_get_contents（）输出显示在Chrome上，但不显示在IE或Firefox上

I am building a php client that sends a get to a server, which sends back a JSON object. I have tried to accomplish this two ways: using the file_get_contents() function or using cUrl. My cUrl code looks like this:

$ch = curl_init($theURL); 
if (! $ch) { 
    die( "Cannot allocate a new PHP-CURL handle" ); 
} 

curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 

$returnedJSON = curl_exec($ch); 

curl_close($ch);

The cool thing is that it works perfectly when I'm using Chrome. However, whenever I try to run the website on IE or firefox, neither method works correctly. Any ideas on why this would be the case?