[FoxMulder]

PHP Code:

AttachParticle(ent, String:particleType[],controlpoint)
{
    //This is used to attach a particle that has two control points
    //such as the medic gun beam. One originates from the medic
    //and the other to its healer
    
    //This particle is attached to the source player
    //This will be visible
    new particle  = CreateEntityByName("info_particle_system");
    
    //This particle is attached to the destination player
    //This will not be visibile, we only need it so the source particle
    //is attached in the apropriate place
    new particle2 = CreateEntityByName("info_particle_system");

    if (IsValidEdict(particle))
    {    
        //Name the originating source, usually the player
        new String:tName[128];
        Format(tName, sizeof(tName), "target%i", ent);
        DispatchKeyValue(ent, "targetname", tName);
        
        //Name the destination, usually another player
        new String:cpName[128];
        Format(cpName, sizeof(cpName), "target%i", controlpoint);
        DispatchKeyValue(controlpoint, "targetname", cpName);
        
        //Name the particle (this particle is attached to the source player)
        new String:particleName[128];
        Format(particleName, sizeof(particleName), "tf2particle%i", particle);
        DispatchKeyValue(particle, "targetname", particleName);
        
        //Tell it what effect name it is then spawn it so we can use it
        DispatchKeyValue(particle, "effect_name", particleType);
        DispatchSpawn(particle);
        
        //--------------------------------------
        new String:cp2Name[128];
        
        //Give the destination particle a unique anme
        Format(cp2Name, sizeof(cp2Name), "tf2particle%i", particle2);
        
        DispatchKeyValue(particle2, "targetname", cp2Name);
        
        //Attach the destination particle to the destined player
        DispatchKeyValue(particle2, "parentname", cpName);
        
        SetVariantString(cpName);
        AcceptEntityInput(particle2, "SetParent");
        
        //Attach the destination particle to the "flag" (stomach area)
        SetVariantString("flag");
        AcceptEntityInput(particle2, "SetParentAttachment");
        //-----------------------------------------------
        
        //Here's where we "join" the two particles
        //Parent the source particle to the source player
        DispatchKeyValue(particle, "parentname", tName);
        SetVariantString(tName);
        AcceptEntityInput(particle, "SetParent");
        
        //Join the source particle to the destination particle
        DispatchKeyValue(particle, "cpoint1", cp2Name);
        
        //Attach the source particle to the "flag" (stomach area)
        SetVariantString("flag");
        AcceptEntityInput(particle, "SetParentAttachment");
        
        //The particle is finally ready
        ActivateEntity(particle);
        AcceptEntityInput(particle, "start");
        
        //PrintToChatAll("Particle 1: %i   Particle 2: %i",particle,particle2);
    }
} 


This is a snippet from some code I have although I haven't used it in a good while so I really don't know how well it works now.
When it was working I would do something like

AttachParticle(Client1, "medicgun_beam_blue" ,Client2)

and that would attach the heal beam from Client 1 to Client 2.

Edit: Damn, I knew this seemed like Déjà vu https://forums.alliedmods.net/showpo...89&postcount=7