Tuesday, June 19, 2012

PHP HTML basic tips, tricks


PHP HTML basic tips and tricks

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.
<?php
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”;
  exit();
}
?> 

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