Display Random Dynamic Content With PHP and XML

in Web Development & Design by — December 21, 2009 at 6:16 am | 0 comments

Every developer, at one point in time, will run into a situation where they need to display a small amount of dynamic data. Why create a whole database? Enter the magical world of XML. XML is easily manageable by anyone who has ever even dabbled a bit in HTML, so understanding should come easily just by looking at an XML file. PHP has classes already set up to parse XML. Here you’ll learn how to use PHP and XML to randomly generate HTML content.

Download the source files. View the demo.

For our example, we have index.php which includes all of the necessary PHP to parse the XML file and generate the content for the viewer. An images folder has 6 images in it, which are referenced in the XML file, home.xml. Let’s start with the XML file, and how to set it up. If you are viewing the demo, just refresh the page and you’ll see different content every time.

<homepage>
	<featured>
		<picture>1.jpg</picture>
		<name>Title 1</name>
		<description>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</description>
	</featured>
</homepage>

So, with XML, every item has to have an opening and closing tag. In our example, we will be creating content from each ‘featured’ block, so you can add as many of these as you like as long as you keep the format the same. Our test XML file just has 6 of these to use. Now, for our PHP, let’s just look at a few lines at a time.

$xml_file = "home.xml";
$xml_picture_key = "*HOMEPAGE*FEATURED*PICTURE";
$xml_name_key = "*HOMEPAGE*FEATURED*NAME";
$xml_description_key = "*HOMEPAGE*FEATURED*DESCRIPTION";

Here we are setting up some variables to tell our script where the XML file is located, as well as how to correctly parse the file. You should create a new variable for each new item you add within the featured blocks.

    function startTag($parser, $data){
        global $current_tag;
        $current_tag .= "*$data";
    }

    function endTag($parser, $data){
        global $current_tag;
        $tag_key = strrpos($current_tag, '*');
        $current_tag = substr($current_tag, 0, $tag_key);
    }

    function contents($parser, $data){
        global $current_tag, $xml_picture_key, $xml_name_key, $xml_description_key, $counter, $featured_array;
        switch($current_tag){
            case $xml_picture_key:
                $featured_array[$counter]->picture = $data;
                break;
            case $xml_name_key:
                $featured_array[$counter]->name = $data;
                break;
            case $xml_description_key:
                $featured_array[$counter]->description = $data;
                $counter++;
                break;
        }
    }

Here we create 3 functions, one to tell the script what to put before the content, one after, and the function to tell it which content block to use. The only thing you’d have to change in this section to apply it to your own work is to add or change each case for each new content in the XML file.

$xml_parser = xml_parser_create();
xml_set_element_handler($xml_parser, "startTag", "endTag");
xml_set_character_data_handler($xml_parser, "contents");

Creating the parser and setting the start tage, end tag, and data handlers. The arguments are the functions that we created earlier.

$fp = fopen($xml_file, "r") or die("Could not open file");
$data = fread($fp, filesize($xml_file)) or die("Could not read file");

Basic PHP file handling functions, that also determine the response if the file is inaccessible

if(!(xml_parse($xml_parser, $data, feof($fp)))){
    die("Error on line " . xml_get_current_line_number($xml_parser));
}

This is the key PHP function that we’re using to parse the file, and if it has an issue it will let you know the line number of the XML file where the problem occurred.

for($y=0;$y<=3;$y++){
    $featured_array = array_values($featured_array);
    $arrayamt = (count($featured_array)-1);
    $x = rand(0,$arrayamt);

    echo "<li>";
    echo "<img src='images/" . $featured_array[$x]->picture . "' width='50' height='50' alt='' />";
    echo "<strong>" . $featured_array[$x]->name . "</strong> &nbsp;&nbsp;";
    echo $featured_array[$x]->description;
    echo "</li>";

    unset($featured_array[$x]);
}

Here is where you will do the majority of customizing to suit your needs. Before this, we had all of the data parsed, placed into an array, and ready to be put somewhere, so that’s what we’re doing now. In our example, we will be generating 4 random list items with content from the XML file.

for($y=0;$y<=3;$y++){
    $featured_array = array_values($featured_array);
    $arrayamt = (count($featured_array)-1);
    $x = rand(0,$arrayamt);

First start a ‘for’ loop. the number 3 is significant because we are starting from 0, since arrays start from 0, and we want to generate 4 random items. Second, array_values() is re-indexing our array each time so that when we remove the current item from the array, we have no holes in our array which prevents the loop from spitting out an empty entry. Next we create a varible that determines the length of the array, so we know how large of a number we can randomly generate. Lastly, we choose a random value from our array between 0 and $arrayamt.

echo "<li>";
echo "<img src='images/" . $featured_array[$x]->picture . "' width='50' height='50' alt='' />";
echo "<strong>" . $featured_array[$x]->name . "</strong> &nbsp;&nbsp;";
echo $featured_array[$x]->description;
echo "</li>";

Here you can figure out where you want to place each item. X is used to determine which number of the array you are getting content from. Follow this format when doing your own work and you should be fine.

    unset($featured_array[$x]);
}

Lastly! We remove the value from the array that we just used with unset(), ensuring that we will not use that same value again the next time the loop runs through. Thanks to Richard for the inspiration on this change.

That’s the end! If you have any questions as usual please leave them in the comments. Thanks to kirupa for providing a tutorial that helped me get started on XML parsing with PHP.

Display Random Dynamic Content With PHP and XML