[JuanStone]

PHP код:

CMD:changepass(playerid, params[])
{
    if(!fexist(UserPath(playerid))) //We checked if you are registered, if it is not would create a file with the password but would have no statistics:
        return SendClientMessage(playerid, -1,"You need to be registred in first.");
    if(isnull(params)) // We note that the text you entered is not null.
        return SendClientMessage(playerid, -1,"USAGE: /changepass [new pass]");
    if(strlen(params) < 3 || strlen(params) > 15) // We note that the text entered is 3 to 15 characters.
        return SendClientMessage(playerid, -1, "Leght the new password incorrect, min 3 characters, max 15.");
    SendClientMessage(playerid, -1, "You hace successfully changed your password."); // message password changed successfully.
    new INI:File = INI_Open(UserPath(playerid)); // Open file the player.
    INI_SetTag(File,"data"); // set tag data if exist write tag.
    INI_WriteInt(File,"Password", udb_hash(params)); // write new password.
    INI_Close(File); // close file.
    return true; // end command.
} 


The code that left @Kaliber would create one file and change the password to a player that is not registered. Forgive me for my bad english, i'm sorry, my native language is another but i try to do my best, sorry .