stock Float: GetZAngleBetweenPoints(Float: x1, Float: y1, Float: x2, Float: y2) {
    return -atan2(x2 - x1, y2 - y1);
}

stock SetPlayerLookAtPlayer(playerid, giveplayerid) {
    new
        Float: pX,
        Float: pY,
        Float: gX,
        Float: gY,
        Float: Z,
    ;
    return
        GetPlayerPos(playerid, pX, pY, Z) &&
        GetPlayerPos(giveplayerid, gX, gY, Z) &&
        SetPlayerFacingAngle(playerid, GetZAngleBetweenPoints(pX, pY, gX, gY))
    ;
}