By the theoretical approach using the full potential linearized augmented plane wave (FP-LAPW) method, the structural, electronic and magnetic properties of zincblende PtxCr1-xP and RhxCr1-xP (x = 0.125 and 0.25) and half Heusler XCrP (X = Pt, Rh)are investigated. From the electronic band structure calculations, CrP in the undoped state at its equilibrium lattice constant of 5.35 angstrom exhibits metallic properties. By doping Pt (/Rh) in 12.5% and 25% doping concentration in the supercell of CrP, the compounds Pt0.125Cr0.875P (/Rh0.125Cr0.875P), Pt0.25Cr0.75P (/Rh0.25Cr0.75P) after optimized volume calculations are observed to be more stable in ferromagnetic phase than that of nonmagnetic phase. On performing the geometric optimization for half Heusler compounds, the ferromagnetic states of XCrP (X = Pt, Rh) are much stable than that of the nonmagnetic and anti-ferromagnetic states. Pt0.125Cr0.875P and Pt0.25Cr0.75P are predicted to exhibit half-metallic ferromagnetism. Rh with 12.5% doping concentration in Rh0.125Cr0.875P is observed to exhibit half-metallic ferromagnetism and for 25% doping concentration in Rh0.25Cr0.75P, metallic properties are predicted. The half Heusler compounds PtCrP and RhCrP exhibit metallic properties in both the spin channels having magnetic moments of 3.01 mu(B) and 2.91 mu(B) respectively. Pt0.125Cr0.875P, Pt0.25Cr0.75P and Rh0.125Cr0.875P exhibit 100% spin polarization with a narrow band gap at the E-F suitable for spin filters and spintronics applications.