Here is my php code
string(13) "1468821556126" int(2147483647)
string(13) "1468821556126" int(1468821556126)
You cannot get a reliable result because your number is too large to be represented as an integer.
echo PHP_INT_MAX; //2147483647 on my system
For a number as large as yours, if you need it in numerical format, cast it to a float instead of an integer
echo floatval('1468821556126'); //1.46882155613E+12