Manually return false for function_exists

Question

I'm having a run at developing a theme options plugin and right now working on implementing a 'hero' header, checking first to see if my plugin is active using:

if( function_exists( 'my_header_function ) ): my_header_function();
else: 
/* carry on and output the default header... */
endif;

Now as my hero header depends on whether the image and logo have been uploaded I wonder if I can manually return a 'false' result from my hook in order to have the original conditional in my header carry on an output the normal header.

Any ideas? Many thanks.

Answer 1

Have your function return your HTML rather than echo it. Perform the logic in the function to see if the image/logo are present and only return the HTML if that's the case, otherwise returning null/false.

function my_header_function( $output = false ) {
     if ( /*image and logo have been uploaded */ ) {
          $output = /* HTML of your hero header */;
     }
     return $output;
}

Add a check to your hook function to see if your function returns content; if it does, echo it.

if ( function_exists( 'my_header_function' ) && ( $hero = my_header_function() ) ) {
     echo $hero;
}