[Konstantinos]

There's not such as parameter 'playerid'. You've to loop through the players, use either foreach (recommended) or normal for loop.

pawn Код:

// Foreach
public autohealth()
{
    new Float:health;
    foreach(playerid : Player)
    {
        GetPlayerHealth(playerid,health);
        if (health < 99.0)
        {
            SetPlayerHealth(playerid, 100.0);
        }
     }
     return 1;
}

pawn Код:

// Normal For Loop
public autohealth()
{
    new Float:health;
    for(new playerid = 0; playerid < MAX_PLAYERS; playerid++)
    {
        GetPlayerHealth(playerid,health);
        if (health < 99.0)
        {
            SetPlayerHealth(playerid, 100.0);
        }
     }
     return 1;
}