Form field validation

Anon

I have been looking thru the manual and some FAQs, and have decided to stop trying to get the hard stuff done first. I am going to try something that appears kinda simple to start out.
Does anyone know how I should go about creating a general field validator? One that merely checks to make sure that every field is non empty before allowing it to submit?
I have seen a few ways with writing code for each field value, but that seems quite ineffeicient, is there a code for checking ALL the fields at once?

And what is the best way to handle that? I mean should I try to add a red astrix next to empty fields, pop up an error message, new page with only missed fields? Personally I don't like popped up error messages, but if it is a better way to go...

mithril

Well,

Glad you don't like pop-up error messages, they're a pet peeve of mine too. Good thing PHP doesn't do silly stuff like that🙂 Seriously, you need client-side capabilities to do those pop-up windows and PHP is strictly server-side. Re-displaying the form and adding a red asterisk, or something equally as noticeable, is a good idea if fields weren't filled in. I'd re-display the entire form, filling the fields with the data the user provided in the previous attempt. You'd have to put all that info into hidden form fields to pass it to the next step anyways, so why not give them the option of editing it? When it comes to validation, remember that arrays are your friends!! Set your form up so that all the fields are array elements, then you just need to run the array through a loop or two to validate all the info you need. It's not simply restricted to checking for empty fields, you can build data-type checking, language filters, and all sorts of fun stuff in.... but let's keep it simple to start with. Try the following script:

<?php

function form($formFields) {

echo "<form action=\"some_page.php\" method =\"post\"><br>\n";
echo " <input type=\"text\" name=\"formFields[one]\" value=\"formFields[one]\"><br>\n";
echo " <input type=\"text\" name=\"formFields[two]\" value=\"formFields[two]\"><br>\n";
echo " <input type=\"text\" name=\"formFields[three]\" value=\"formFields[three]\"><br>\n";
echo " <input type=\"text\" name=\"formFields[four]\" value=\"formFields[four]\"><br>\n";
echo " <input type=\"text\" name=\"formFields[five]\" value=\"formFields[five]\"><br>\n";
echo " <input type=\"submit\" name=\"submit\" value=\"Submit this form\"><br>\n";
echo "</form><br>\n";

}

function validate($formFields) {

// loop through the passed array, making sure that all fields are filled
while (list($key,$var) = each($formFields)) {

// if the current field is empty
if ($var == "") {

// print an error message and re-display the form, filling it with existing data
echo "You have not filled in all the boxes. Try again.<br>";
form($formFields);

// tell the rest of the function not to execute and exit this loop 
$continue = false;
break;

}

// if the current field isn't empty
else {

 // add the field's data to a string
 $str .= "Form field $key = $var<br>";

// allow the rest of the function to continue executing
$continue = true;

}

// if all fields were filled (ie. $continue is equal to boolean true)
if ($continue) {

// print the string created in the loop
echo $str;

}
}

// if the form has been submitted
if ($submit) {

// call the validation function, passing in the form data
validate($formFields);
}

// if the form hasn't been submitted, display the form
else {

form();
}

This is obviously very simplistic and not a "real-world" example, but it should hopefully get you started in the right direction. Info on the list() and each() functions used in the while loop structure are found in the manual at:

http://www.php.net/manual/en/function.list.php
http://www.php.net/manual/en/function.each.php

respectively. HTH!!

Cheers,

Geoff A. Virgo

mithril

Opps!! I'm getting brain-to-finger farts tonite. The following code snippet from my example:

// if the form hasn't been submitted, display the form
else {

form();
}

should read:

// if the form hasn't been submitted, display the form
else {

form("");
}

The orignal code will give you an error about "missing argument 1 for function form()". This will fix it🙂

Geoff

Anon

you should check out my form validator (javascript) .. it checks all the fields in a form independent of the number of form elements. it skips hidden fields, and i've also built in a check on characters which may not be entered (like < and >). You can find it in the source of http://phoenix.atomicvoid.net/forum.php

Anon

Thank you. This looks great. Other than that one alert in Dutch, of corse, luckily I speak a little as I just happen to be working here in Holland. So I modified it a bit, but I think I must have done something wrong...as I can't get it to work.
This is what it now looks like, What did I mess up, or is there merely somewhere I am suuposed to call part of it?
<script language="javascript">
function checkForm()
{
var cntr = 0;
var ready = true;

while ((cntr < document.forms[0].elements.length) && (ready))
{
var fieldType = document.forms[0].elements[cntr].type;

if ((document.forms[0].elements[cntr].value == "") && (fieldType != "hidden") && (fieldType == "text"))
{
alert("Not all fields have been completed. Please try again.");
return false;
break;
}

else
{
if (replaceChars( document.forms[0].elements[cntr] ))
{
cntr ++;
}
else
{
alert("Please don't use bracket or quote characters, thanks!");
ready = false;
break;
}
}
}
return ready;
}

Anon

Okay, Quick question about yours. I like it, and I like no alerts.
But I have a few questions about yours and how it works. I have programmed beofer(though into it php) so I get the loops and arrays.
I can't test this yet, my server was supposed to be ready tuesday mornning, it is now 1:30pm on thursday, but as soon as it is, it will have php and I can test it.
I think I can tell pretty much what to change to make it fit for my form. Except for all the background and formatting and whatnot. It needs to fit in with the style of the rest of the intranet.
These questions are very newbie, and I am sorry.
1)Do I have a form page? That makes it doesn't it? and what is the action="php page" supposed to have on it? To be general about this, basically I am asking how once i get it modified to the right forms and adresses and action to I incorporate it into the site? I assume i save it all as a .php3(or 4 depending on what my server admin has set up) and then make calls to it somwhere, is this right?

2)How would I add the red astrix after fields that are empty have been found as empty and the page in re-loaded? I know I am supposed to add some sort of
echo "<font color=/"red/">*</font>" thing, but where exactly does that go? Probably in an if statement somwhere in that loop right?

I think that will cover my questions for now, at least until I can see it, and possibly get something to work.

Anon

humz .. strange it works fine over here .. but with this script, you can't work with an <input type=submit> (submit button for a form), beacause this will submit the form, without calling the javascript function, so you have to use a normal button with an onclick="javascript:submit();" event or a link similar to this : <a onfocus=this.blur(); href=javascript:submitForm();>insert message</a> to call the function that checks the form.

If you can't find the problem, you can give me an URL where i can have a look for the problem.

Greetz!

kparker

Before you get too excited about a javascript validator, please remember that JS can be turned off by the user (and often is precisely for the purpose of suppressing all the popup junk that too many sites seem to be in love with.)

So unless you are working on an intranet app, where you can have some say in what users do with their browser, you need to view any JS features as being user-convenience (validation happens much sooner) and certainly do not depend on it for validating what actually goes into your database.

mithril

Regarding the first question:

You can integrate a form/response set of functions in a couple ways. The easiest is to simply make the action of the form the file that contains all the functions and use the if structure to determine which function is called. The easiest method of achieving this is to pass the $PHP_SELF variable into the form, either by declaring it global in the top of the function (ie. global $PHP_SELF😉 or by passing it in as a function arugument. Once you have access, set "action=\"$PHP_SELF\"" and your form will always be targeted at the current page, regardless of what the page's filename is.

Your second option, the more common method, is to save the functions in a separate file which you then include into whatever page you need. If you're targeting the form at a separate file, make sure you include the function file there as well.

Regarding your second question:

The easiest way to control the display of the red asterisks is to create a second argument in the form function, say $error. The function would be called from the main script by passing emtpy vars for both arguments:

form("","");

and from within the field validation function by:

form($formFields,true);

for example. Simply change the form to somthing like:

<?php
....

if (is_array($formFields) && $error == true) {

// print something here to indicate a missed field

}

echo " <input type=\"text\" name=\"formFields[one]\" value=\"formFields[one]\"><br>\n";

.....
?>

Since the missing field indicators won't print unless the some form data and an error are indicated, this is a simple way of making your function fulfill two needs based on the varying conditions. This is an extremely simple example that would need a good deal of fluffying out before it could be used in an application, but it should serve to illustrate one method of doing this. As for making it fit into the intranet, PHP outputs HTML code. You can either hardcode the attributes you wish to see or use CSS to make it adapt. Part of the initial learning curve of PHP is learning how to write one language with another while trying to think effectively in both. It's really not that hard once you get used to it🙂 The next step is then learning how to abstract the 2 so that your webpages are written in HTML and the PHP really does only the backend stuff. That's the harder part. HTH.

Cheers,

Geoff A. Virgo