Here are some commands we will be using to get the details of the events or actions we perform.
This gives us the length of the array or the number of elements present in the array. If we know we are using 5 checkboxes then we can directly use the number 5 but it is a good to use this as this picks up all the checkboxes of the group without missing any checkbox. Note that the word scripts in the document.form1.scripts.length is the name of the array and same as the checkboxes name.
The above command will return true if the checkbox is checked so we will use one if condition to know it is checked or not. The value of i is the index of the array and as we will be using one for loop so the value of i will be changing upto the maximum value. All Checking & Un checking in a group of checkboxes by single button
More on CheckBox & PHP
Checkbox: Using checkbox with PHP Scripts
Validation: Checking the user input of a checkbox and showing message
Checkbox Array: Handling a group of checkbox by array
Disable checkbox: Disable and enable checkbox by clicking button
Disable Text box : Disable a textbox by a checkbox
Limit Checkbox : Limiting the number of checkbox can be checked by user
Check All : Checking or unchecking a group of checkbox by button or at single point