[Konstantinos]

You cannot use this and get it works.

pawn Code:

new pVariable=0[MAX_PLAYERS];

You should define it as a global variable and set a value after, either inside a callback/custom function or command.

pawn Code:

// Global variable
new 
    pVariable[ MAX_PLAYERS ]
;

// OnPlayerConnect
pVariable[ playerid ] = 0;

// There you want to increase the value by one
pVariable[ playerid ]++;