Snippets to add conditional rendering for custom attrs: {has_foo}print foo{/has_foo}

WP_CALENDAR_CONDITIONAL_RENDERING.php

// see https://wp-events-plugin.com/documentation/conditional-placeholders/
// for the conditional funcs that we have out of the box

// see https://wp-events-plugin.com/tutorials/creating-conditional-placeholders-for-events/
// for how to introduce conditional funcs for custom attributes
// the docs explain what each each variable means
function em_event_output_condition_filter($replacement, $condition, $match, $EM_Event){
    // Checks for has_FOO conditional
    if(is_object($EM_Event) && preg_match('/^has_(FOO)$/', $condition, $matches)){
        if(array_key_exists($matches[1], $EM_Event->event_attributes) && !empty($EM_Event->event_attributes[$matches[1]]) ){
            $replacement = preg_replace("/\{\/?$condition\}/", '', $match);
        }else{
            $replacement = '';
        }
    }
    // Checks for no_FOO conditional
    if(is_object($EM_Event) && preg_match('/^no_(FOO)$/', $condition, $matches)){
        if(!array_key_exists($matches[1], $EM_Event->event_attributes) || empty($EM_Event->event_attributes[$matches[1]]) ){
            $replacement = preg_replace("/\{\/?$condition\}/", '', $match);
        }else{
            $replacement = '';
        }
    }
    //Return the result
    return $replacement;
}

// this is super weird syntax, but it what registers the func that will parse has_foo/no_foo 
add_filter('em_event_output_condition', 'em_event_output_condition_filter', 1, 4);


// Here is another example: https://pastebin.com/4amjiMwi
// Here's where we would paste the PHP snippet – http://wp-events-plugin.com/tutorials/how-to-safely-add-php-code-to-wordpress/