[Adil]

First of all put this on the top of your script, below the #define's.

pawn Код:

new PlayerMaterials[MAX_PLAYERS];

then change your old command to this one:

pawn Код:

if(strcmp(cmd, "/500mats", true) == 0)
{
    PlayerMaterials = 500;
    SendClientMessage(playerid, COLOR_RED, "You got 500 Materials");
    return 1;
}
return 1;

Why did you privided so useless information in your script ? you didn't even used GetPlayerName.