在PHP5.5中找不到SQLite3

I feel like I MUST be missing something. By all documentation, SQLite3 is included in PHP versions above 5.3, and yet I can't seem to get it going. Below is the very simplest test I could come up with. Did Ubuntu 14.04's package of php have it removed for some reason? Am I spelling it wrong over and over? Do I fundamentally misunderstand how to copy/paste? Thanks in advance!