We report the results of radar observations of near-Earth asteroid 54509 (2000 PH5) in July 2001 with the Goldstone 8560 MHz (3.5 cm) radar and in July 2004 and 2005 with the Arecibo 2380 MHz (13 cm) radar. We present a shape model and spin state description for 2000 PH5 using radar data inversion of 231 high resolution delay-Doppler images and 156 continuous wave spectra as well as 20 optical lightcurves collected from 2001 to 2005. From the radar echo bandwidths, we determine the mean radius to be 64 ± 4 meters with a retrograde pole at ecliptic longitude and latitude (173, -81) with an uncertainty in latitude of ± 8 degrees and an obliquity of 169 degrees. We also find that the lightcurves cannot be linked in phase via a single constant sidereal spin rate. To link the lightcurves we must introduce a linear increase in the sidereal spin rate equivalent to ~0.3 deg/day over 4 years. Our initial sidereal spin rate for the epoch of July 27, 2001 is 42582.4 deg/day or a sidereal period of 0.20290 hr. This necessary increase in spin rate can be attributed to thermal Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) torques that can also drive the spin axis to its observed orientation and account for the already rapid 12.2 minute spin period of 2000 PH5.