Custom Theme Fields in Settings Menu - apply filters to one of those fields?

Question

I found an interesting concepts of adding an additional option to the "General Options" in Wordpress.

/**
 * Custom Theme Settings
 * see http://digwp.com/2009/09/global-custom-fields-take-two/
 */

add_action('admin_menu', 'add_gcf_interface');

function add_gcf_interface() {
    add_options_page('Other', 'Other', '8', 'functions', 'otherGlobalOptions');
}

function otherGlobalOptions() {
    ?>
    <div class='wrap'>
    <h2>Sonstiges</h2>
    <form method="post" action="options.php">
        <?php wp_nonce_field('update-options') ?>
        <p><strong>Welcome Message</strong><br />
        <textarea name="welcomemessage" cols="100%" rows="7"><?php echo get_option('welcomemessage'); ?></textarea></p>
        <p><input type="submit" name="Submit" value="Save" /></p>
        <input type="hidden" name="action" value="update" />
        <input type="hidden" name="page_options" value="welcomemessage" />
    </form>
    </div>
    <?php
}

This works just fine.

I'm just wondering now if there is a chance to apply a filter to that input?

Like I can do add_filter('the_content', 'wr_replace_text', 100); I want to do

add_filter('welcomemessage', 'wr_replace_text', 100);

Is that somehow possible, because this doesn't work for me at the moment.

Kind regards, Matt

Answer 1

You can create a custom filter using filter functions of Plugin API. I have changed you code as following to create and use custom filter.

function add_gcf_interface() {
add_options_page('Other', 'Other', '8', 'functions', 'otherGlobalOptions');
}

function otherGlobalOptions() {
?>
<div class='wrap'>
<h2>Sonstiges</h2>
<form method="post" action="options.php">
    <?php wp_nonce_field('update-options') ?>
    <p><strong>Welcome Message</strong><br />
    <textarea name="welcomemessage" cols="100%" rows="7"><?php echo apply_filters('welcomemessage',get_option('welcomemessage')); ?></textarea></p>
    <p><input type="submit" name="Submit" value="Save" /></p>
    <input type="hidden" name="action" value="update" />
    <input type="hidden" name="page_options" value="welcomemessage" />
</form>
</div>
<?php
}
// Create custom filter
function add_welcomemessage($welcomemessage) {   
return $welcomemessage;
}
add_filter('welcomemessage', 'add_welcomemessage');

Tell me whether it worked for you or i will provide another solution.

Answer 2

I would like to strongly recommend you to read these articles:

• The Complete Guide To The WordPress Settings API, Part 1: What It Is, Why It Matters
• The Complete Guide To The WordPress Settings API, Part 2: Sections, Fields, and Settings
• The Complete Guide To The WordPress Settings API, Part 3: All About Menus
• The Complete Guide To The WordPress Settings API, Part 4: On Theme Options
• The Complete Guide To The WordPress Settings API, Part 5: Tabbed Navigation For Your Settings Page
• The Complete Guide To The WordPress Settings API, Part 6: Menu Pages
• The Complete Guide To The WordPress Settings API, Part 7: Validation, Sanitisation, and Input I
• The Complete Guide To The WordPress Settings API, Part 8: Validation, Sanitisation, and Input II

During reading these articles, you will find an interesting proper concepts of adding an additional option to the "General Options" in WordPress and much more useful information.