ZAB Controller described a confused clearance event involving the GEELA 4 RNAV STAR and the absence of clear phraseology that captures route information but not any 'descend via' inference.

Narrative

It was a busy arrival push into PHX this morning. With the new GEELA 4 RNAV arrival there is quite a bit more transmissions that need to be made to ensure the pilot will do what we need him to do. If the pilot is to descend via the arrival; well that's a straight forward clearance. When we have to vector the aircraft for sequencing the phraseology to put the aircraft back on the arrival is very confusing. An A320 was issued a clearance to cross GEELA at and maintain 12;000 FT and 250 KTS. The pilot read this back correctly. The pilot was then issued 'Cleared the GEELA 4 arrival; Runway 7R transition'. The pilot read back 'Cleared for the GEELA 4 arrival; 7R transition.' At no point was a descend via clearance given or read back. The aircraft then entered PHX Approach and said he was descending 'VIA' the arrival. PHX Approach then called us and let us know. We need to come up with some type of phraseology that will allow us to clear the aircraft for the arrival and transition without the pilot thinking he is cleared to 'DESCEND VIA' the arrival. It seems the pilots are associating the runway transition with a descend via clearance. Maybe give the runway transition on initial check on if that is legal..