Juanfra Aldasoro on "[Runtime Error?] Fatal error: Call to undefined function is_user_logged_in()"

Hi there,

I'm writing a plugin in which I relate some posts and data.

I'm having the following problem:

- I have a function ie: prefix_get_post_by_meta(), and it contains something like:

function prefix_get_post_by_meta( $meta_value ){

	$args = array(
					'numberposts'	=> 1,
					'post_type'	=> 'my_post_type',
					'meta_key'		=> 'my_key',
					'meta_value'	=> $meta_value
				);

	// get results
	$the_query = new WP_Query( $args );

	// The Loop
	if ( $the_query->have_posts() ) :
		while ( $the_query->have_posts() ):
			$the_query->the_post();
			return get_the_ID();
		endwhile;
	endif;

	wp_reset_postdata();

	return false;
}

Everything goes great with that function.

The problem is that at certain point when I use this function in another function for a shortcode or in the front end it doesn't return anything.

Imagine I have another function my_shortcode_function()

function my_shortcode_function(){

       $my_id = prefix_get_id_from_api(); // this gives a unique ID that match with the custom field value
       $the_post_id = prefix_get_post_by_meta( $my_id );
       $output = '';

       if ( $match_id ){

           $output .= '<h1>' . get_the_title( $the_post_id ) . '</h1>';
	   $output .= '<h1><a href="'. get_permalink( $the_post_id ) .'">' . get_the_title( $the_post_id ). '</a></h1>';

      }else{
           $output .= 'Nothing for the ID ' . $my_id;
      }

      return $output;

}

add_shortcode( 'my_shortcode_function', 'my_shortcode_function' );

----
If I invoque the function directly from the shortcode, I get nothing as a response, when the post actually exists.

If I modify the function to echo the $output, and add that as an action for the init:

add_action( 'init', 'my_shortcode_function' );

I get the accurate result on the backend. On the front end, I get the wrong result.

----

If I stay with the echo instead of returning the $output, and I call the function directly on my plugin, like

my_shortcode();

Then I get this:

Fatal error: Call to undefined function is_user_logged_in() in /Applications/MAMP/..../wp-includes/query.php on line 2778

It's obvious that is a runtime thing. Is there something that I'm missing?

Every query function end up using WP_Query(), that's why I assumed that this wasn't the problem, am I right? (I tried with get_posts just in case and the same happened).

any help is super appreciated :)

Juanfra.