How to make plugin required in a wp theme without using php conditional statements when calling an individual function from that plugin?

One of my WordPress themes requires a few third party plugins to run correctly.

Most of the times I used to call functions from third party plugins using conditional statements like

    if(function_exist('plugin_function')) {
             plugin_function() // do something
    }

suppose though I need to use extensively one plugin through many files of my theme… I would like to avoid using many IF conditions… is there a proper way to require certain specific plugin to be installed in WP or even better install them if they’re missing before activating the theme?

thanks

is_plugin_active() is rather fragile: it will break when either the plugin author renames the main file or when the user renames the plugin’s directory or main file. It’s better to check if a certain public function exists.

To avoid having to make that check each time you need some of the plugin’s functionality, you could show a message in the admin area:

add_action( 'admin_notices', 'my_theme_dependencies' );

function my_theme_dependencies() {
  if( ! function_exists('plugin_function') )
    echo '<div class="error"><p>' . __( 'Warning: The theme needs Plugin X to function', 'my-theme' ) . '</p></div>';
}

Another alternative is to use something like http://tgmpluginactivation.com/