Why is conditionally loading a custom plugin's code only on a specific custom post type causing the site content to disa

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I'm working on a fill-in-the-blanks plugin () which has been working.

I realized that the plugin was loading its styles, js, and inserting a div on every page, not just its own custom post type ('lqdnotes). So I used a simple if statement to ensure the code is only passed if the cpt is present.

It occurs in the following locations:

lqd-notes.php

function lqdnotes_enqueue_css() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdcssversion = filemtime( LQDNOTES_DIR . 'public/css/lqdnotes.css' );
        wp_enqueue_style(
            'lqdnotes-css',
            plugins_url(  'public/css/lqdnotes.css', __FILE__ ),
            array(),
            $lqdcssversion
        );
    }
}

add_action( 'enqueue_block_assets', 'lqdnotes_enqueue_css' );

public/display-filled.php

function lqdnotes_enqueue_display_filled() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdfilterinputversion = filemtime( LQDNOTES_DIR . 'public/js/lqdnotes-filter-inputs.js' );
        wp_enqueue_script(
            'lqdnotes-filter-inputs',
            LQDNOTES_URL . 'public/js/lqdnotes-filter-inputs.js',
            array( 'jquery' ),
            $lqdfilterinputversion
        );

        $ajax_array = array(
            'ajax_url' => admin_url( 'admin-ajax.php' )
        );

        wp_localize_script(
            'lqdnotes-filter-inputs',
            'lqdnotes_ajax',
            $ajax_array );
    }
}
add_action( 'wp_enqueue_scripts', 'lqdnotes_enqueue_display_filled' );

public/modify-display.php

function lqdnotes_enqueue_display_blanks() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdfilterspanversion = filemtime( LQDNOTES_DIR .'public/js/lqdnotes-filter-span.js' );
        wp_enqueue_script(
            'lqdnotes-filter-spans',
            plugin_dir_url( __FILE__ ) . 'js/lqdnotes-filter-span.js',
            array(),
            $lqdfilterspanversion
        );
    }
}
add_action( 'wp_enqueue_scripts', 'lqdnotes_enqueue_display_blanks' );

function lqdnotes_add_div( $content ) {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $updated_content = '<div id="message-notes" class="message-notes">' . $content . '</div>';
        return $updated_content;
    }
}
add_filter( 'the_content', 'lqdnotes_add_div' );

When I activate the plugin and browser to a page of content (say test.liquidchurch) the header and footer display but no page content..and this is occurring on pages that aren't part of the CPT.

If, however, I open one of the CPT pages everything displays correctly (see /).

To see what a page on test.liquidchurch should look like go to liquidchurch. As one can see, there is content for the page and if I were to disable the notes plugin on test.liquidchurch it would appear there as well (I've disabled the plugin on the live site until this is resolved).

I'm working on a fill-in-the-blanks plugin (https://github/liquidchurch/lqd-notes) which has been working.

I realized that the plugin was loading its styles, js, and inserting a div on every page, not just its own custom post type ('lqdnotes). So I used a simple if statement to ensure the code is only passed if the cpt is present.

It occurs in the following locations:

lqd-notes.php

function lqdnotes_enqueue_css() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdcssversion = filemtime( LQDNOTES_DIR . 'public/css/lqdnotes.css' );
        wp_enqueue_style(
            'lqdnotes-css',
            plugins_url(  'public/css/lqdnotes.css', __FILE__ ),
            array(),
            $lqdcssversion
        );
    }
}

add_action( 'enqueue_block_assets', 'lqdnotes_enqueue_css' );

public/display-filled.php

function lqdnotes_enqueue_display_filled() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdfilterinputversion = filemtime( LQDNOTES_DIR . 'public/js/lqdnotes-filter-inputs.js' );
        wp_enqueue_script(
            'lqdnotes-filter-inputs',
            LQDNOTES_URL . 'public/js/lqdnotes-filter-inputs.js',
            array( 'jquery' ),
            $lqdfilterinputversion
        );

        $ajax_array = array(
            'ajax_url' => admin_url( 'admin-ajax.php' )
        );

        wp_localize_script(
            'lqdnotes-filter-inputs',
            'lqdnotes_ajax',
            $ajax_array );
    }
}
add_action( 'wp_enqueue_scripts', 'lqdnotes_enqueue_display_filled' );

public/modify-display.php

function lqdnotes_enqueue_display_blanks() {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $lqdfilterspanversion = filemtime( LQDNOTES_DIR .'public/js/lqdnotes-filter-span.js' );
        wp_enqueue_script(
            'lqdnotes-filter-spans',
            plugin_dir_url( __FILE__ ) . 'js/lqdnotes-filter-span.js',
            array(),
            $lqdfilterspanversion
        );
    }
}
add_action( 'wp_enqueue_scripts', 'lqdnotes_enqueue_display_blanks' );

function lqdnotes_add_div( $content ) {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $updated_content = '<div id="message-notes" class="message-notes">' . $content . '</div>';
        return $updated_content;
    }
}
add_filter( 'the_content', 'lqdnotes_add_div' );

When I activate the plugin and browser to a page of content (say test.liquidchurch) the header and footer display but no page content..and this is occurring on pages that aren't part of the CPT.

If, however, I open one of the CPT pages everything displays correctly (see https://test.liquidchurch/blog/notes/breakthrough/).

To see what a page on test.liquidchurch should look like go to liquidchurch. As one can see, there is content for the page and if I were to disable the notes plugin on test.liquidchurch it would appear there as well (I've disabled the plugin on the live site until this is resolved).

• custom-post-types
• plugin-development
• filters
• hooks

Share Improve this question asked Dec 20, 2019 at 17:25 davemackeydavemackey 31522 silver badges1818 bronze badges

Add a comment  | 

2 Answers 2

Sorted by: Reset to default 1

I realize you've already answered your issue. However, I think there is some additional explanation possible to give more clarity to the issue and the solution.

The issue is your lqdnotes_add_div() function. This is hooked to a filter - the_content.

In WordPress, any time you use a filter, your filter function must return a value for the item being filtered. This might be a string, array, or boolean. In this case, $content is a string, and a string must be returned.

Your filter function only returned a value if the post type was "lqdnotes". In all other cases a null value was returned.

While you do need to return a value for $content, you do not need to do this with an else condition. In fact, it is a good standard practice to make sure there is at least a return value at the end of any filter function to provide for returning an unfiltered result if any of the function's other conditions are not met.

function lqdnotes_add_div( $content ) {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $updated_content = '<div id="message-notes" class="message-notes">' . $content . '</div>';
        return $updated_content;
    }
    return $content;
}
add_filter( 'the_content', 'lqdnotes_add_div' );

StackOverflow may be my rubber duck. Almost immediately after publishing the question the solution popped into my mind.

The problem was in the function lqdnotes_add_div. This function took $content (the post content) as a parameter. If post was not of type lqdnotes then it didn't perform any operation on $content...or so I thought.

PHP actually returns null if a return value is not specified, so actually was performing an action on $content - setting it to null.

Add an else clause that explicitly returns the $content I received fixes the issue:

function lqdnotes_add_div( $content ) {
    if ( get_post_type( get_the_ID() ) == 'lqdnotes' ) {
        $updated_content = '<div id="message-notes" class="message-notes">' . $content . '</div>';
        return $updated_content;
    } else {
        return $content;
    }
}

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