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best way to check if button pressed and text box as no value

Posted on 2006-06-15
Medium Priority
Last Modified: 2008-03-06
Hi what is the best way to check an empty text box

at the moment im using

if ($_POST['sel_search'] && $_POST['prt_list']==""){

            elseif ($_POST['prt_list']!=""){


thanks in advance
Question by:avo42
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Expert Comment

ID: 16916126
I'm not sure you can get much better than what you have.
LVL 29

Assisted Solution

TeRReF earned 200 total points
ID: 16916173
Well, to rule out spaces, you could use:
if ($_POST['sel_search'] && trim($_POST['prt_list'])==""){

          elseif (trim($_POST['prt_list'])!=""){


Assisted Solution

ljubiccica earned 200 total points
ID: 16916183

i would use
if(isset($_POST['sel_search']) && $_POST['prt_list']=="")

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Assisted Solution

Autogard earned 200 total points
ID: 16916185
My only suggestion would to stay consistent in your code.  If you are checking == "" and != "" I would also use:

if ($_POST['sel_search'] != ""
LVL 49

Accepted Solution

Roonaan earned 500 total points
ID: 16917607
I would suggest:

if(isset($_POST['sel_search']) && !empty($_POST['prt_list'])) {


Assisted Solution

ixti earned 400 total points
ID: 16917789
In addition to comments above:

1. If form was submitted from your site and form has text box named 'my_text', then even i it will be empty on submit, then it will be always set. So you don't have to check every field is it was set or not. I mean:
    // We need to check if one of fields were submitted only once, just to be sure
    // if form was submitted. You can give a name to submit button, so you'll be able
    // to check if form was submitted, but for me it's much easier to check one of
    // input fields, just because i never use value of submit buttons.
    if (isset($_POST['var1'])) {
      $error = array();
      if ('' == trim($_POST['var1'])) $error[] = 'Var1 is empty';
      if ('' == trim($_POST['var2'])) $error[] = 'Var2 is empty';
      if ('' == trim($_POST['var3'])) $error[] = 'Var3 is empty';
      if ('' == trim($_POST['var4'])) $error[] = 'Var4 is empty';
      if (0 < count($error)) {
        foreach($error as $msg) echo 'Error: ' . $msg . '<br />\n';
      } else {
        // ... here we can do any actions with submitted data ... :))

  <form method="POST">
  <input type="text" name="var1" />
  <input type="text" name="var2" />
  <input type="text" name="var3" />
  <input type="text" name="var4" />
  <input type="submit" value="submit" />

2. The main what you have to do is to check where from was processed from, just to encrease security. I suggest you to read PHP Security Guide (http://phpsec.org/projects/guide/) for getting more info about security in PHP.

3. You can use my simple class to process forms: http://www.experts-exchange.com/Web/Web_Languages/PHP/PHP_Databases/Q_21776115.html#16424179 It's undocumented but it's really simple, and you'll find an example there wich will explain almost everything :))

Assisted Solution

aminerd earned 300 total points
ID: 16917856
Also, remember that == does not compare types; consider:

$test = 0;
if ($test == '') echo 'Nothing';

$test = NULL;
if ($test == '') echo 'Nothing';

$test = FALSE;
if ($test == '') echo 'Nothing';

You'll get three "Nothing"s. NULL and FALSE may not be an issue, but if you need to allow for zeros, you'll want to try a different route. For instance, the === operator, which IS type-sensitive.

Expert Comment

ID: 16917931
Values processed by form is always STRINGS. So if you'll use type-sensitive === operator then you'll have some troubles.

For example:
<input type="text" name="int" />
<input type="submit" value="go" />

if you'll enter 123 to this form and press submit button, you'll have:
$_GET['int'] = '123';
not integer 123, but string '123':

if ($_GET['int'] === 123) { echo 'This won't work anyway!'; }
if ($_GET['int'] === '123') { echo 'This works!'; }
if ($_GET['int'] == '123') { echo 'And this works!'; }
if ($_GET['int'] == 123) { echo 'And this works too!'; }

If you will not input anything in that field, then $_GET['int'] will be '', not NULL:
if ($_GET['int'] === NULL) { echo 'This won't work anyway!'; }
if ($_GET['int'] === '') { echo 'This works!'; }
if ($_GET['int'] == '') { echo 'And this works!'; }

And if you'll put false (or true) in that field, it will also be 'false' or 'true', noy bollean false ore true:
if ($_GET['int'] === false) { echo 'This won't work anyway!'; }
if ($_GET['int'] == false) { echo 'This won't work too!'; } // Note this!
if ($_GET['int'] === 'false') { echo 'This works!'; }
if ($_GET['int'] == 'false') { echo 'And this works!'; }

Assisted Solution

mazzachre earned 200 total points
ID: 16918809
If you are concerned about performance on the server I would use a small javascript to test the fields before submitting the form.

Author Comment

ID: 16919833
Hi all

what would be the simplyes method to do that as i dont know javascript at all

thanks all for your input
LVL 49

Expert Comment

ID: 16919848
You cannot rely on javascript solely. Mazzachre should know better.

There are plenty people who are not using javascript and therefor can enter unvalidated data unless you also validate serverside.


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