Spawn an entity after a specific phrase is said in chat

[Dorpz]

Right, so I'm trying to work out a way to spawn an entity by saying a phrase in chat,
for instance if I said "!ball" it'd spawn a ball in front of me.

I think I know how to do the spawning bit, but I have no bloody idea how to do the bit with the chat.

Do any of you know how I could go about making this thing?

Also, sorry if this is the wrong section to ask this, I don't post here enough.

[Stalinalive]

heres an example

hook.Add( "PlayerSay", "Killurself", function( ply, text, public )
	text = string.lower( text ) -- Make the chat message entirely lowercase
	if ( text == "Im gay" ) then -- the text your looking for in chat
		npc:Spawn() -- call the function
		return "" -- this will make the IM gay text not  show up in chat but still spawns the npc
	end
end )

This is Serverside Btw for the Clientside Equivalent use [URL="https://wiki.garrysmod.com/page/GM/OnPlayerChat"]OnPlayerChat[/URL]