The hybridization of P in ${\mathrm{PO}}_4^{3-}$is same as in

No. of hybrid orbitals(H.O)=1/2(No. of valence electrons on central atom + no. of monovalent atoms-                                                                          Charge)

${\mathrm{PO}}_4^{3-}$ : no. of hybrid orbitals= 1/2(5+3)=4 --- sp³ hybridization

${\mathrm{ICl}}_4^{-}$ : no. of hybrid orbitals= 1/2(7+4+1)=6 --- sp³d² hybridization

SO₃ : no. of hybrid orbitals= 1/2(6)=3 --- sp² hybridization

${\mathrm{NO}}_3^{-}$ : no. of hybrid orbitals= 1/2(5+1)=3 --- sp² hybridization

${\mathrm{SO}}_4^{2-}$ : no. of hybrid orbitals= 1/2(6+2)=4 --- sp³ hybridization