Starcraft 2: Photon Cannon Detection Range?

So I was rushing with a Dark Templar and a nearby Photon Cannon couldn't shoot me, but his troops shot me.

Can this Photon Cannon detect me even if it can't shoot me? Because his Stalkers shot me even though there were no other Detects flying around.

Is the Photo Cannon’s detection range just really long or is this guy cheating?

its detection range is equal to its sight range, its attack range is 7 and its sight range is 11

edit: from Team Liquid wiki: 1 range is about the size of a zergling

No, this guy is not cheating! On the topic of Detectors Liquidpedia says the following:

Although detection is tied to a unit's sight range, it will provide detection within that range when its own line of sight is blocked as long as vision is provided by another unit, e.g. Missile Turret at the bottom of a ramp with a Marine on top of said ramp; this will detect Dark Templars on the upper cliff level.

This means all structures that have the Detector abilitie are able to see your cloaked or burrowed units even if they can not attack it. Having larger sight (and with that detection) range than attack range is something all static defense buildings have in common:
Protoss' Photon Cannon, Terrans Missile Turret and Zergs Spore Crawler all have a sight range of 11 and attack range of 7. Missle Turrets attack range can be upgraded to 8 with Hi-Sec Auto tracking