preg_match语法

Question

Studying some code from a codeigniter tut, the following preg_match pattern has me baffled:

preg_match('/js$/', $include)

What is the purpose of the $ after the js?

Thanks for the always thoughtful replies!

-----Complete Code-----

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/**
 * Layouts Class. PHP5 only.
 *
 */
class Layouts {

  // Will hold a CodeIgniter instance
  private $CI;

  // Will hold a title for the page, NULL by default
  private $title_for_layout = NULL;

  // The title separator, ' | ' by default
  private $title_separator = ' | ';

  public function __construct()
  {
    $this->CI =& get_instance();
  }

  public function set_title($title)
  {
    $this->title_for_layout = $title;
  }

  public function view($view_name, $params = array(), $layout = 'default')
  {
    // Handle the site's title. If NULL, don't add anything. If not, add a
    // separator and append the title.
    if ($this->title_for_layout !== NULL)
    {
      $separated_title_for_layout = $this->title_separator . $this->title_for_layout;
    }

    // Load the view's content, with the params passed
    $view_content = $this->CI->load->view($view_name, $params, TRUE);

    // Now load the layout, and pass the view we just rendered
    $this->CI->load->view('laytous/' . $layout, array(
      'content_for_layout' => $view_content,
      'title_for_layout' => $separated_title_for_layout
    ));
  }

  public function add_include($path, $prepend_base_url = TRUE)
  {
    if ($prepend_base_url)
    {
      $this->CI->load->helper('url'); // Load this just to be sure
      $this->file_includes[] = base_url() . $path;
    }
    else
    {
      $this->file_includes[] = $path;
    }

    return $this; // This allows chain-methods
  }

  public function print_includes()
  {
    // Initialize a string that will hold all includes
    $final_includes = '';

    foreach ($this->includes as $include)
    {
      // Check if it's a JS or a CSS file
      if (preg_match('/js$/', $include))
      {
        // It's a JS file
        $final_includes .= '<script type="text/javascript" src="' . $include . '"></script>';
      }
      elseif (preg_match('/css$/', $include))
      {
        // It's a CSS file
        $final_includes .= '<link href="' . $include . '" rel="stylesheet" type="text/css" />';
      }

      return $final_includes;
    }
  }
}

Answer 1

The dollar is an "end of string" anchor. The match will only succeed if "js" is at the end of the string.