The ornamental design for a portablefoodheater, as shown and described.
FIG. 1 is a first perspective view of a portable food heater showing my design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a bottom view thereof; and,
FIG. 9 is an enlarged view of the selected portion in FIG. 2.
The broken lines shown in the drawings depict portions of the portable food heater in which the design is embodied that form no part of the claimed design.