Coupling constant in 1H NMR with phosphorus
Yes, this is the 2JP-H coupling. You could verify this (if you had access to a NMR spectrometer) by running a 1H{31P} experiment; that is, a proton with 31P decoupling. This doublet would collapse back to a singlet. You would also notice some changes to the phenyl protons, as they all have some coupling to the 31P also. A 2J coupling of 13.5Hz is very typical for this type of 1H-31P coupling.

The magnitude of 1H-31P couplings varies enormously, depending on bond order, oxidation state of 31P and bonding arrangement. 


1JPH of PH3 = ~175Hz.
1JPH of HP(O)(OMe)2 = ~1200Hz
2JPH P(CHx)y are typically 1-20Hz 


It is sometimes observed in 31P-1H (and 31P-13C) that high bond order couplings are larger than lower bond order couplings (ie 3JPH > 2JPH)