Passing Array Using Html Form Hidden Element

May 6, 2007

Html form hidden element is used to pass information which is not visible to the user but used internaly by underlying scripts. For example the status of the process or step of multi step form submission. PHP array is an important language structure used in manipulation of multiple values associated with single object. Sometimes it is required to pass these values accross the pages between browser and the server. Following method can be used to pass PHP Arrays using html form hidden elements.

Using individual array element

This method uses seperate hidden element for each element in array. This can be done by following method.

foreach ($my_array as $key => $value)
 echo ‘<input type=hidden name=”my_array[]” value=”‘.htmlspecialchars($value).'”>’;

This will generate an array in html form. And when submitted can be accessed by form handling PHP script using following code.
$my_array = $_POST[‘my_array’];

Combining all array elements in one value to hidden element

In this method all elements in an array are combined in single value using implode() PHP function. implode() will return a string combining all the array elements in the same order, seperated by given string. Then this combined value can be passed in html form hidden element. See below.
$single_value = implode(“,”, $my_array);
echo ‘<input type=hidden name=”single_value” value=”‘.htmlspecialchars($single_value).'”>’;

And when submitted the array can be retreived using explode() PHP function. explode() will return an array by spliting the string using the given seperator. See code below.
$my_array = explode(“,”,$_POST[‘single_value’]);

PHP HTML basic tips and tricks

January 30, 2007

PHP is an HTML-embedded scripting language. The goal of the language is to allow web developers to write dynamically generated pages quickly. In the course of web development of using PHP PHP and HTML interact a lot. PHP can generate HTML, and HTML can pass information to PHP.

Encoding/decoding when passing a data through a form or URL
Certain characters, for example ‘&’, have special significance in HTML, and should be represented by HTML entities if they are to preserve their meanings. There are several stages for which encoding is important. Assuming that you have a string $data, which contains the string you want to pass on in a non-encoded way, these are the relevant stages.

Passing a value through HTML FORM you must include it in double quotes, and htmlspecialchars() the whole value. For exampe see the code below

<?php echo “<input name=’data’ type=’hidden’ value=’” . htmlspecialchars($data) . “‘>”; ?>

While passing a value through URL you must encode it with urlencode(). It will convert all non-alphanumeric characters except -_. with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. See example below.
<?php echo “<a href='” . htmlspecialchars(“/nextpage.php?stage=23&data=” .urlencode($data) . “‘>\n”; ?>

Creating a PHP arrays in a HTML form

To get your FORM result sent as an array to your PHP script you name the INPUT, SELECT, TEXTAREA elements like this:
<input name=”MyArray[]“>
<input name=”MyArray[]”>
<input name=”MyArray[]”>
<input name=”MyArray[]”>

If you do not specify the keys, the array gets filled in the order the elements appear in the form. Above example will contain keys 0, 1, 2 and 3. Notice the square brackets after the variable name, that’s what makes it an array. You can group the elements into different arrays by assigning the same name to different elements:
<input name=”MyArray[]“>
<input name=”MyArray[]”>
<input name=”MyOtherArray[]“>
<input name=”MyOtherArray[]”>
This produces two arrays, MyArray and MyOtherArray, that gets sent to the PHP script. It’s also possible to assign specific keys to your arrays:
<input name=”AnotherArray[]”>
<input name=”AnotherArray[]”>
<input name=”AnotherArray[email]“>
<input name=”AnotherArray[phone]”>

The AnotherArray array will now contain the keys 0, 1, email and phone.

Getting results from a select multiple HTML tag.
The select multiple tag in an HTML construct allows users to select multiple items from a list. These items are then passed to the action handler for the form. The problem is that they are all passed with the same widget name. I.e.
<select name=”var” multiple=”yes”>
Each selected option will arrive at the action handler as var=option1, var=option2, var=option3. Each option will overwrite the contents of the previous $var variable. The solution is to use PHP’s “array from form element” feature. The following should be used:
<select name=”var[]” multiple=”yes”>
Now first item becomes $var[0], the next $var[1], etc.

Passing a variable from Javascript to PHP
Since Javascript is a client-side technology, and PHP is a server-side technology, the two languages cannot directly share variables. It is, however, possible to pass variables between the two. One way of accomplishing this is to generate Javascript code with PHP, and have the browser refresh itself, passing specific variables back to the PHP script. The example below shows precisely how to do this — it allows PHP code to capture screen height and width, something that is normally only possible on the client side.
if (isset($_GET[‘width’]) AND isset($_GET[‘height’])) {
  // output the geometry variables
  echo “Screen width is: “. $_GET[‘width’] .”<br />\n”;
  echo “Screen height is: “. $_GET[‘height’] .”<br />\n”;
} else {
  // pass the geometry variables
  // (preserve the original query string
  //   — post variables will need to handled differently)

  echo “<script language=’javascript’>\n”;
  echo ”  location.href=\”${_SERVER[‘SCRIPT_NAME’]}?${_SERVER[‘QUERY_STRING’]}”
            . “&width=\” + screen.width + \”&height=\” + screen.height;\n”;
  echo “</script>\n”;

HTML Form Elements Values usage Examples in PHP

January 28, 2007

During the development of interactive web sites using PHP and HTML it is requiredto deal with data flow between user/browser and the server. This is achieved by using HTML forms and supporting HTML form elements. Following examples shows how these form elements can be used in HTML andPHP to allow interaction between user and the server.

Text input HTML form element

This input form element can be used for a single lime text input from the user. For example user first name, user e-mail, phone numbers etc. The syntax in HTML form is as below

<input type=”text” name=”username”>
<input type=”text” name=”email”>

This will display an input box in the browser and the values of this element canbe accessed at the form handling php script by following.
<?php echo “User Name:”.$_POST[‘username’]; ?>

Password type. The defulat type of HTML input element is text. The special password type of input can be used as following
<input type=”password” name=”password”>

and can be accessed in PHP similar to above input element.
<?php echo “The Password is:”.$_POST[‘password’]; ?>

Hidden type. The hidden field is used to send information from browser to the server without having to input it. Typically this is used to send some logical data that has nothing to do with user but used at the server in PHP program logic. For example state, action, or passing the result to the other module etc. Please note that you encode the value using htmlspecialchars() function.
<input type=”hidden” name=”action” value=”<?php echo htmlspecialchars(‘step2’); ?>”>

and the value of this field can be accessed in PHP by following.
<?php echo “The Value of action is:”.$_POST[‘action’]; ?>

Textarea multiline text HTML form element

This form element can be used for a multi-line text input from the user. For example product description. The syntax is as below.

<textarea name=”description” rows=”5″ cols=”50″></textarea>

This will display a multi-line input area in the browser and the size can be controlled using rows and cols tag. The text value input by user can be accessed in PHP by following

<?php echo “Product Description:”.$_POST[‘description’]; ?>

Select (Pull Down menu) and Select multiple HTML form element

This type of HTML form element is used to allow user to select from multiple choices. For example selecting a month or a day. The html syntax is as below.

<select name=”year”>
<option value=”2004″>2004</option>
<option value=”2005″>2005</option>
<option value=”2006″>2006</option>
<option value=”2007″>2007</option>
<option value=”2008″>2008</option>

The value of selected choice can be accessed in form handling PHP script as following
<?php echo “Selected Year is:”.$_POST[‘year’]; ?>

The variation to this allows user to select multiple choices from the given options.
This can be done by following select multiple syntax

<select multiple name=”colors[]” size=”4″>
<option value=”Red”>Red
<option value=”Yellow”>Yellow
<option value=”Blue”>Blue
<option value=”Green”>Green
<option value=”White”>White
<option value=”Black”>Black

The size tag can be used to control how many rows should be visible. And note the use of ‘[]’ following the name of the select box. This will denote that it is an array and the choices can be accessed in form handling PHP script by following.

foreach ($_POST[‘colors’] as $key => $value) {
echo “Key: $key; Value: $value<br>”;
If Red and Green is selected then above code will print
0: Red
1: Green

Radio button HTML form element

Radio button in HTML form is an alternative method that allows user to select from given options. Unlike drop down menu this is used to create more visibilty in the input form.

<input type=”radio” name=”colour” value=”Red”>Red
<input type=”radio” name=”colour” value=”Orange”>Orange
<input type=”radio” name=”colour” value=”Blue”>Blue

The value of the selection can be accessed in PHP as following
<?php echo “Selected Color is:”.$_POST[‘colour’]; ?>

Check Box button HTML form element

This is an alternative way of allowing user to select multiple choices from the given options. Following example show the use of Check Boxes in an HTML form

<input type=”radio” name=”colour[]” value=”Red”>Red
<input type=”radio” name=”colour[]” value=”Orange”>Orange
<input type=”radio” name=”colour[]” value=”Blue”>Blue
<input type=”radio” name=”colour[]” value=”Violet”>Violet
<input type=”radio” name=”colour[]” value=”Black”>Black

Again here PHP array is used to access the selected choices from the user.
foreach ($_POST[‘colors’] as $key => $value) {
echo “Key: $key; Value: $value<br>”;

If Red and Violet is selected then above code will display
0: Red
1: Violet