convert large integeer to binary Little-Endian php

Question

I want convert 365 decimal to binary (each number four bytes) So i convert:

pack("s*",1); // output .... , in hexedidor: 01000000

And this is the correct output But when conver 365 :

pack("s*",365); // output m... in hexeditr:6D000100

But I expect 6D010000 How can I get that conclusion? example output I need 1

my code :

$content= pack("s*",365);
file_put_contents("file.txt",iconv("UTF-8","UTF-16LE",$content));