[Chdata]

I see all sorts of ugly stuff like setting the targetname of players to something temporarily.

It's really simple.

PHP Code:

stock SetParentEx(iParent, iChild)
{
    SetVariantString("!activator");
    AcceptEntityInput(iChild, "SetParent", iParent, iChild);
}

// player "eyes" "righteye" "lefteye" "partyhat" "head" "flag"
// weapon "muzzle" "eject_brass"
stock SetParent(iParent, iChild, const String:szAttachment[] = "", Float:vOffsets[3] = {0.0,0.0,0.0})
{
    SetVariantString("!activator");
    AcceptEntityInput(iChild, "SetParent", iParent, iChild);

    if (szAttachment[0] != '\0') // Use at least a 0.01 second delay between SetParent and SetParentAttachment inputs.
    {
        SetVariantString(szAttachment); // "head"

        if (!AreVectorsEqual(vOffsets, Float:{0.0,0.0,0.0})) // NULL_VECTOR
        {
            decl Float:vPos[3];
            GetEntPropVector(iParent, Prop_Send, "m_vecOrigin", vPos);
            AddVectors(vPos, vOffsets, vPos);
            TeleportEntity(iChild, vPos, NULL_VECTOR, NULL_VECTOR);
            AcceptEntityInput(iChild, "SetParentAttachmentMaintainOffset", iParent, iChild);
        }
        else
        {
            AcceptEntityInput(iChild, "SetParentAttachment", iParent, iChild);
        }
    }
}

stock bool:AreVectorsEqual(Float:vVec1[3], Float:vVec2[3])
{
    return (vVec1[0] == vVec2[0] && vVec1[1] == vVec2[1] && vVec1[2] == vVec2[2]);
} 


iChild is the entity that will be made to follow wherever iParent moves.