$myFile = "example.com/json/";
$jsonfile = "/home/example/public_html/example.json";

file_put_contents($jsonfile, ""); //empties the file


try
{

$cache_buster = date("YmdHi");
$footerdata = 'example.com/example.json?v='.$cache_buster;

//Get data from existing json file
$jsondata = file_get_contents($myFile);

//write json data into data.json file
if(file_put_contents($jsonfile, $jsondata)) {
echo 'Data successfully saved';
}
else
echo "error";

}
catch (Exception $e) {
echo 'Caught exception: ',  $e->getMessage(), "n";
}