In the html form you must to name de checkbox group like chkFruit[] (all checkbox as this), so in php script you will get the array $chkFruit.
The array contains: Array Length (sizeof($chkFruit)).
If the user checks two checkbox, you'll get the values by $chkFruit[0] and $chkFruit[1].
You may use the array functions to extract data in the best mode for you.