[GangstaSunny]

PHP код:

new id;
new string[126];
if(sscanf(params, "u", id)) return SCM(playerid, -1, ""SCMD"/check [ID/Name]");
if(!IsPlayerConnected(id))
{
    format(string,sizeof(string),"Params: 'id' is '%d'",id);
    SendCllientMessage(playerid,-1,string);
} 


Just for debug. I recommend to use debug-method before asking here.