How to get the permanent link in a plugin?

Question

I'm writing a plugin to add some extra contents that contain the permanent link to the (single) post.

function abcd_add_contents($content) {
    $extra_content = the_permalink();

    if (is_single()) {
         $content .= $extra_content;
    }
    return $content;
}

add_filter('the_content', 'abcd_add_contents');

the_permalink() does not work. How can I obtain the permanent link information of the current post in this plugin function?

Answer 1

globalize $post to get the current post's data. also, you want get_permalink, which returns the permalink, rather than the_permalink, which directly echoes the permalink.

function abcd_add_contents($content) {

    if (is_single()) {
        global $post;
        $extra_content = get_permalink( $post->ID );
        $content .= $extra_content;
    }
    return $content;
}

add_filter('the_content', 'abcd_add_contents');

Answer 2

the_permalink function echoes the post permalink. What you want to use is get_permalink function, which returns post permalink for use as variable.