Page 273 - Beginning PHP 5.3

Chapter 9: Handling HTML Forms with PHP
data is not sent to the server. Sometimes the field is sent as an empty string; sometimes no field name is
sent at all. The following table illustrates the behavior of various form controls when they ’ re not filled in
or selected:

Form Control What Happens When It ’ s Not Filled In Or Selected

Text input field The field name is sent, along with an empty value.
Password field The field name is sent, along with an empty value.
Checkbox field Nothing is sent at all.

Radio button field Nothing is sent at all.
Submit button Nothing is sent at all if the button isn ’ t clicked. This can happen if the user
presses Enter/Return to submit a form. However, if there ’ s only one submit
button in the form, most browsers will still send the button ’ s field name
and value.

Reset button Nothing is ever sent.
File select field The field name is sent, along with an empty value.
Hidden field The field name is sent, along with an empty value.

Image field Same behavior as a submit button.
Push button Nothing is ever sent.
Pull - down menu Impossible to select no option, so a value is always sent.

List box Nothing is sent at all.
Multi - select box Nothing is sent at all.

Text area field The field name is sent, along with an empty value.

Why is this important? Well, when nothing is sent at all for a field, PHP doesn ’ t create an element for the
field in the $_POST , $_GET , or $_REQUEST array. So if you attempt to access the element, you ’ ll generate
a PHP notice along the lines of:
PHP Notice: Undefined index: gender in process_registration.php on line 18

This notice might appear in your server ’ s error log, or in the browser window, depending on your error
reporting settings. Such notices won ’ t interfere with the running of your script; for example, in the case
just shown, all that happens is that an empty string is passed to the echo() statement:

<dt>Gender</dt><dd><?php echo $_POST[“gender”]?></dd>

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