Simplifying PHP forms that pre-populate with dabase data and error check, so actively overwrite with $_POST data

Ok, so this is a common scenario.

You have an html form that involves editing information. The original information comes from the database. When you post the form, it may not save the information immediately, because something may need fixing when the data-checking is done, maybe one of the required fields is left blank. As a result, you want to redisplay the form field, but if there was post data, display the post data, if not, display the original data from the database.

So I created a function to check post, then default to some arbitrary data (in this case from the database).

But overall, the approach feels inelegant, the POST data is being pulled invisibly inside the function from a global, but i开发者_C百科f I pass the post data in I have to pass it in for every function call, and it's almost as verbose as just doing it by hand each time, so specifically I'm looking for alternatives to this approach, and generally I'd love advice on better ways to deal with this form scenario that I deal with every single time I edit html forms.

// Pull from post or get, or else use data, e.g. from the database, to populate a form.
function in_or_data($index, $data, $trim=false){
    return $_POST[$index]? ($trim ? trim($_POST[$index]) : $_POST[$index]) : $data[$index];
}

<?php
$item_name = in_or_data('item_name', $data_from_database_somewhere); // Pull post data, with defaults coming from the 
?>

// ..... Later, some example html that just escapes & echoes out the data. .....
<td id='item-name'><input name="item_name" type="text" id="item_name" value="<?php echo escape($item_name); ?>" size="47" maxlength="100" tabindex="9"></td>

How can I improve dealing with forms that get their data either from the database initially, or from post after some kind of submission is being done?

<input type="text" name="abc" value="<?php array_key_exists('abc', $_REQUEST) ? $_REQUEST['abc'] : "default value goes here" ?>" />

A more elegant solution, though a serious amount of work, would involve using ajax (jquery, etc.) to perform server-side validation on the form BEFORE actually submitting.

What you are doing seems fine to me. Basically what I do in the same situation is have a hidden field in the form something like

<input name="is_edit"` ... />

and in my PHP just check for $_POST['is_edit'] so that I don't populate anything from the database. One problem with doing every field individually like you are doing it above is that for certain things (for example checkboxes) if the user doesn't check the checkbox, $_POST['checkbox_data'] is not going to be set, so I believe you would end up pulling that from the database using the function you have above. It should be either all or nothing that is pulled by the DB. I therefore do something like this:

<?php
if (isset($_POST['is_edit'])) {
    $var1 = $_POST['var1'];
    $var2 = $_POST['var2'];
    // etc
}
else {
    $data = do_db_query_and_get_data();
    $var1 = $data['var1'];
    $var2 = $data['var2'];
    // etc
}
?>
<input type="something" value="<?php echo $var1; ?>" />
<input type="something" value="<?php echo $var2; ?>" />
<input type="hidden" name="is_edit" value="1" />

Doing it like this also has the other advantage of not having to do the database query unless it is necessary.

In addition to my initial php code, I have started using the html5 attributes like required and setting the html5 form types like number, email, etc. It has really really made my forms much better for browsers that support html5 form aspects, and it degrades to standard text boxes and ignores the required attribute in browsers that don't support html5 form stuff.