src/SimplePlugin.php
public function get_path($file = '') {
        if (!defined('WP_PLUGIN_DIR')) {
            wp_plugin_directory_constants();
        }

        // TODO There is probably better constant than WP_CONTENT_DIR!
        $path = WP_PLUGIN_DIR . DIRECTORY_SEPARATOR . $this->id;
        if (!empty($file)) {
            $path .= DIRECTORY_SEPARATOR . $file;
        }

        return $path;
    }
public function get_path($file = '') {
        if (!defined('WP_PLUGIN_DIR')) {
            wp_plugin_directory_constants();
        }

        // TODO There is probably better constant than WP_CONTENT_DIR!
        $path = WP_PLUGIN_DIR . DIRECTORY_SEPARATOR . $this->id;
        if (!empty($file)) {
            $path .= DIRECTORY_SEPARATOR . $file;
        }

        return $path;
    }
Returns path to the plugin's directory. If `$file` is provided
than is appended to the end of the path.

@since 0.1.3
@param string $file (Optional).
@return string