php - file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known

I'm trying to download an image from a server using a PHP script on my website on xampp server.

The image is being downloaded using the function file_get_contents.

The php code for downloading on the server is:

if(isset($_GET['path']) && isset($_GET['username'])) {
    echo "path:".$_GET['path'];
    $temp = explode(".", $_GET['path']);
    $extension = end($temp);
    $fname="images/".$_GET['title'];
    $filenameIn  = $_GET['path'];
    $filenameOut = "" . $fname;

    $contentOrFalseOnFailure   = file_get_contents($filenameIn);
    $byteCountOrFalseOnFailure = file_put_contents($filenameOut,$contentOrFalseOnFailure);
}

But I'm getting this error:

Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed: Name or service not known in
/opt/lampp/htdocs/xampp/project/upload_art.php on line 19

Warning: file_get_contents(http://app6.pixlr.com/_temp/528afa6e2f7cc6a5b1000101.jpg):
failed to open stream: php_network_getaddresses: getaddrinfo failed:
Name or service not known in
/opt/lampp/htdocs/xampp/project/upload_art.php on line 19

I have checked out all posted answers here but none seems to resolve the issue. Please help!