so please can u check this ?  
  
function purchaseAmmo() 
    local weapons = getPlayerWeapons( player, weaponSlot) 
    local currentWeaponAmmo = getPedTotalAmmo( player, getSlotFromWeapon(weaponID)) 
    local totalAmmo = currentWeaponAmmo+weaponAmmo 
    if ammoType == "magazine" then 
        if currentWeaponAmmo then 
        setWeaponAmmo( player, weaponID, currentWeaponAmmo+weaponAmmo) 
        end