Often when writing something for the web, you’ll need to output data in a table (or, for CSS zealots, nicely formatted <div>’s).  In order to improve readability, you might want to colour every second row differently. This is really easy:

$counter = 1;
while($counter < 10) {
 
    //set bgcolor
    $bgcol = ($counter % 2 == 1) ? "#ececec" : "#ffffff";
 
    //write the output html
    echo "<tr><td bgcolor=\"".$bgcol."\">Your content goes here...</td></tr>";
 
    //increment the counter
    $counter++;
}

The above code is merely to illustrate the idea behind alternating rows.  I’ve used a very short conditional that checks if the current row is even or odd.  Based on that result, it sets the background colour variable to either #ffffff or #ececec.  Once the loop has run, the counter is incremented, and we start over.

By the way, the line:

    $bgcol = ($counter % 2 == 1) ? "#ececec" : "#ffffff";

is equivalent to using:

    if ($counter % 2 == 1) {
        $bgcol ="#ececec";
    }
    else {
        $bgcol = "#ffffff";
    }

Some extensions to make this code better are things like inserting real data (from a call to a database), replacing the table code with <div>’s, replacing the bgcolour values with a particular style class, and writing to a string/file/etc instead of echoing the results.  Another cool thing (if in a user-based environment) is to add a subsequent if statement that checks to see if the row being processed matched the currently logged on user - this way you can show a user that the row in question belongs to them by defining a third bg colour and highlighting it differently to the rest.

A slightly more real-world example of how the code may look is:

$sql = "SELECT id, name, surname FROM person";
$result = mysql_query($sql);
$counter = 1;
 
while($row = mysql_fetch_array($result)) {
 
    //set class
    $classname = ($counter % 2 == 1) ? "dark-div" : "light-div";
 
    //write the output html
    echo "
        <div class=\"".$classname."\">
            <div>". $row['id'] ."</div>
            <div>". $row['name'] ."</div>
            <div>". $row['surname'] ."</div>
        </div>";
 
    //increment the counter
    $counter++;
}

And in next week’s issue, how to assemble a nuclear bomb from ordinary household items!

This entry was posted on Monday, June 23rd, 2008 at 10:00 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.