PHP allows you to name multiple form elements with the same name (appended by square brackets):
<form name='myForm'> <input type='text' name='myInput[0]' id='myInput[0]' /> <input type='text' name='myInput[1]' id='myInput[1]' /> <input type='text' name='myInput[2]' id='myInput[2]' /> </form>
When you submit this, the $_REQUEST['myInput'] variable becomes an array with all the values from your input boxes. But how do you access these input boxes in Javascript? You can't do:
document.forms['myForm'].elements.myInput[0]
because the square brackets are illegal in an identifier in Javascript, even though they are legal in HTML. (In fact, that would try to access the 0th element of the myInput array, which doesn't exist.) Instead, you can use the array notation for accessing a property of an object:
document.forms['myForm'].elements['myInput[0]']
Since myInput[] is now being passed in as a string, and not a JS identifier, you're fine.