Use php to validate a html form

Question

I am trying to validate a html form using php. I have solved it in one like below:

Part of my html form:

  <input class="text" type="text" name="fname" id="firstname1"  required="required">

And at the signup.php I have

<?php

    if (!preg_match("/^[a-zA-Z ]*$/",$_POST['fname']))
  {
  echo ('Name should include only characters'); 
  die( '</body></html>' );
  } 
  ?>

But my problem is that in this form the error message does not appear at the same page with the form, but in another page. I want to have the error message appear at the page where the form is.

In javascript I make it this way, but I don't know how to make this in php: I build a function like below:

function name() {

    var pass = document.getElementById('firstname1');
    var sb = document.getElementById('submit1');
    var letters=/^[a-zA-Z]+$/;
    if (pass.value.match(letters) ){
     sb.disabled = false;
     document.getElementById('error-fname1').style.display = 'none';
        }
    else {
         document.getElementById('error-fname1').style.display = 'block';
        sb.disabled = true;  }
          }

and then I try to call it in this way:

<input class="text" type="text" name="fname" id="firstname1"  required="required" onchange="name()">

<span class="errorformat "  id="error-fname1"  style="display: none" >
          Please write only letters
                    </span>

Please help me...I am trying to learn php... Thanks in advance

Are you setting the action of the form to another page? If so, the only way you could put an error message on the old page with the server-side PHP code is by redirecting back to the old page. — Anonymous
– Anonymous, Commented Feb 7, 2014 at 21:01
yes when I press submit button i go to another page that said: succesor output the error message. This page is called signup.php and there I also connect the form with the database and there i chack for errors. But how can I check for errors in the page where i have the form so in signup.html page? — user3272713
– user3272713, Commented Feb 7, 2014 at 21:04
You can't simply check on the same page using PHP. The whole point of PHP is that it is a sever-side code. — Anonymous
– Anonymous, Commented Feb 7, 2014 at 21:05
You can do it using AJAX request, but you will need javascript and PHP. — MamaWalter
– MamaWalter, Commented Feb 7, 2014 at 21:06

PixelAcorn · Accepted Answer · 2014-02-07 21:09:23Z

1

Why don't you validate it on the same page.

php:

if(isset($_POST['fname'])){
  ... (Any checks you want to make)
}

html:

<form action="" method="post">
<input class="text" type="text" name="fname" id="firstname1"  required="required">
</form>

That way, the php runs only if the form has been submitted, and the error will appear on the same page.

answered Feb 7, 2014 at 21:09

PixelAcorn

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12 Comments

Anonymous Over a year ago

The form is meant to go to a different page, but the error message should be shown on the old page.

MamaWalter Over a year ago

just redirect to the next page validation succeeded

user3272713 Over a year ago

Yes @Jaxon, what I have in mind is to make it in the same page with the form...I try to build a php function, and call it onchange...Because I want that when I click at the second input form and the first is not correct, to show the error...not to show the error at the end when I pres submit...But how can I do this?

Anonymous Over a year ago

You would need JavaScript for that but don't you already have a JavaScript validation?

user3272713 Over a year ago

Yes I have. But I was thinking which one to use. I am learning php now and I was thinking to make validation with php. But is is better in my case?

|

malta · Accepted Answer · 2014-02-07 21:10:55Z

0

If you want to carry out server side validation using php (which is highly recommended), then you can use the following approach by placing everything in the same file ... example file form.php

<?php

//validate form

if(!preg_match("/^[a-zA-Z ]*$/",$_POST['fname']))
{ 
$problem = true;
}
else
{
$formok = true;

?>

then the html part starts and you can at some point put your error message:

<?php if($problem) echo "Incorrect Name Format" ?>

<?php if($formok) echo "Nice job" ?>

then the form should be like this:

<form action="form.php">
//inputs
</form>

answered Feb 7, 2014 at 21:10

malta

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Comments

Anonymous · Accepted Answer · 2014-02-07 21:11:22Z

0

If you wanted to use a redirect to show the error message on the page before, you can do something similar to this:

if (!preg_match("/^[a-zA-Z ]*$/",$_POST['fname'])) {
    header("Location: http://domain/oldpage.php");
    exit();
}

You could have it redirect to a new error page or possibly include a query string at the end of the link such as ?error=true. Then, check on the page for that query string and if it is there, display the error message.

answered Feb 7, 2014 at 21:11

Anonymous

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Comments

codeguerrilla · Accepted Answer · 2014-02-07 21:15:31Z

0

On the page where your form is at, add a GET var and check if it is set. Something like:

if(isset($_GET['error'])) {
   // Output error message logic here. Don't forget to sanitize the GET var //
}

In your file where you are handling the data, if you have any errors, header the user back to the page with your form with the error message attached.

$errormsg = '';
if($_POST['fname'] == trim("") || !isset($_POST['fname'])) {
  $errormsg = 'Please enter your name';
  header('location: signup.php?error='.$errormsg);
}

This assumes the page with your form is a PHP file. If it is not, just change the extension.

answered Feb 7, 2014 at 21:15

codeguerrilla

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