How to Use Conditional Logic to Control Content Display in WordPress

Many WordPress users want to display specific content, like info boxes or author lists, only when certain conditions are met. This is a common request for creating dynamic, context-aware websites. However, implementing this conditional logic can be tricky, especially when dealing with PHP, custom fields, and taxonomies like categories and tags.

Why Conditional Logic Can Be Difficult

The core challenge is that WordPress is built to be flexible, but this means the logic for controlling content often needs to be custom-coded. Users frequently run into issues where:

• They attempt to use CSS for a task that requires server-side PHP processing.
• Their custom PHP functions have flaws in logic, such as only checking the authors of posts on the current page rather than all posts in a category.
• They need to check the value of a custom field (like a checkbox) but are unsure how to properly integrate that check into an existing function.

Common Solutions for Conditional Content

1. Using PHP Conditional Tags for Categories and Tags

To show or hide content based on the category or tag being viewed, you must use PHP within your theme's template files (e.g., sidebar.php). CSS alone cannot query the database to check these conditions.

Example: To display an info box only when viewing a specific category, you would wrap the content in a conditional check.

<?php
if ( is_category( 'x' ) ) { // Replace 'x' with your category ID, slug, or name
    ?>
    <div class="info-box">
        <p>This is my category-specific content.</p>
    </div>
    <?php
}
?>

Important: This code must be placed in a PHP file on your server. Relying on AI tools for code snippets can often lead to incorrect advice, such as suggesting CSS for a PHP task. Always test code in a staging environment first.

2. Checking Custom Field Values (e.g., a Checkbox)

If you need to check whether a custom field is set or not—for example, to apply a discount only if a specific checkbox is not checked—you need to retrieve that meta value and use it in a conditional statement.

Example: The following code checks for a custom field named 6_checkbox and only applies a discount if the field is empty.

<?php
// Get the value of the custom field '6_checkbox'
$checkbox_status = get_post_meta( $post->ID, '6_checkbox', true );

// Apply discount only if $discount_post is not empty AND the checkbox is NOT checked
if ( ! empty( trim( $discount_post ) ) && empty( $checkbox_status ) ) {
    // Your code to apply the discount goes here
}
?>

3. Creating Mutually Exclusive Taxonomy Choices

By default, the WordPress category and tag interfaces use checkboxes, allowing multiple selections. If you need subcategories to be mutually exclusive (behaving like radio buttons where only one can be selected), this requires a significant customization.

Why it's complex: This is not a default WordPress behavior. Achieving it involves two major steps that go beyond simple theme editing:

1. Altering the UI: Using JavaScript to change the checkboxes in the post editor meta box to radio buttons.
2. Altering the Data Processing: Adding custom server-side code to ensure WordPress correctly handles the radio button data upon saving a post.

Due to the complexity, this is often best handled by an experienced developer to avoid conflicts with other plugins or themes.

Key Takeaways

• Use the Right Tool: For server-side logic (checking categories, custom fields), you must use PHP. CSS is for styling only.
• Test Thoroughly: When writing custom functions, ensure they query all relevant data (e.g., all posts in a taxonomy, not just paginated results) to avoid incomplete information.
• Consider Complexity: Some features, like changing the fundamental UI of the post editor, are advanced and require a robust understanding of WordPress hooks and JavaScript.

By understanding these core concepts, you can more effectively implement the dynamic, conditional content that makes your WordPress site unique.