Solution: extend CB to E, make EB=CB, and connect DE to AB in P, then DE is the minimum value of the sum of PC+PD.

∵AD∨BE，

∴∠A=∠PBE,∠ADP=∠E，

∴△ADP∽△BEP，

∴AP:BP=AD:BE=4:6=2:3，

∴PB=32PA，

And ∵PA+PB=AB=5,

∴PB=35AB=3.