Valid value for the "name" attribute in HTML

Issue

I use PHP to get radio button values from an HTML page. My HTML looks like this:

<input type="radio" name="1.1" value="yes">
<input type="radio" name="1.1" value="no">

<input type="radio" name="1" value="yes">
<input type="radio" name="1" value="no">

The result is that $_POST['1'] returns a value, but $_POST['1.1'] returns nothing. I checked the HTML 4 specifications, say value for the name attribute only starts with a letter, but 1 is not a letter. How come it gets returned while 1.1 does not? Or is there some other magic happening here? I use the latest version of Chrome.

Solution

By HTML rules, the name attribute may have any value: it is declared with CDATA type. Do not confuse this attribute with the references to attributes declared as having NAME type. See 17.4 The INPUT element, name = cdata [CI].

In the use of $POST[...] in PHP, you need to note this PHP rule: “Dots and spaces in variable names are converted to underscores. For example <input name="a.b" /> becomes $_REQUEST["a_b"].” See Variables From External Sources.

So $_POST['1'] should work as is and does work, but instead of $_POST['1.1'] you need to write $_POST['1_1'].

Answered By - Jukka K. Korpela