FIG. 1 is a front left side perspective view of a headlamp for a vehicle showing my new design; FIG. 2 is a front right side perspective view thereof; FIG. 3 is a rear side perspective view thereof; FIG. 4 is a front elevational view thereof; FIG. 5 is a rear elevational view thereof; FIG. 6 is a left side elevational view thereof; FIG. 7 is a right side elevational view thereof; FIG. 8 is a top plan view thereof; and, FIG. 9 is a bottom plan view thereof.