How to remain number as string in PHP

i have created services that request FB for real-time updates. The result that return by Facebook is in JSON type. Its like this:

{"object":"page","entry":[{"id":"248874468652581","time":1428654497,"changes":[{"field":"feed","value":{"item":"comment","verb":"add","comment_id":"248878481985513_367520770121283","parent_id":"248874468652581_248878498652178","sender_id":1490984774509544,"created_time":1428654497,"sender_name":"Orlig Anbiz","message":"helo"}}]}]}

Then i want to keep all data in this JSON to store in database. My problem is at

"sender_id":1490984774509544,

Which is the sender id (number without double qoutes). Then when I put this sender_id in var, it is automatically convert it into float. My php code:

$sender_id = strval($json_array['entry'][0]['changes'][0]['value']['sender_id']);
echo nl2br("The Sender ID = $sender_id \n");

My result for sender_id will become like this:

The Sender ID = 1.4909847745095E+15

I dont want that sender ID change to float but keep as string which is supposed to display like this:

The Sender ID = 1490984774509544

Please Help. Thank You in advance.