My first wordpress plugin

I choose a new wordpress template some days ago, it looks good. But have some problems like this. I spent about four hours to do this, because I know little about php and had never written wordpress plugins. Now I think it is very interesting to write the plugin. So I want to introduce it.

Where to get start?

First, I know I will filter the source, so I regist the filter with this function:

add_filter('the_content','filter_shrink');

The “the_content” is the filter’s name, and filter_shrink is my filter function, I will write it later. Then I should could change the width and height from option page, so I write:

add_action('admin_menu', 'flash_zoom_options_page');

This function told wordpress I will regist a menu in “admin_menu” with the flash_zoom_options_page function.

implements the functions

Now let’s see the filter_shrink:

function replaceSize($matches)
{
  global $flashzoom_settings;
  $replaceStr = ' width="'.$flashzoom_settings['target_width'].'" height="'.$flashzoom_settings['target_height'].'" ';
  return $matches[1].$replaceStr.$matches[3].$replaceStr.$matches[5];
}

function filter_shrink($content) {
    global $flashzoom_settings;
    if(is_home()){
      $content = preg_replace_callback(
           '|(<'.'object.*)(width="d*"s*height="d*")(.*)(width="d*"s*height="d*")(.*</object>)|',
            "replaceSize",
            $content);
    }

    return $content;
}

Look at the “$flashzoom_settings”, it is the length and height that stored in wordpress. I just use preg_replace_callback function to replace the origin width and height. The php regexp is strange, especially the usage of “|”.

Then we can see the flash_zoom_options_page function:

function isInteger($input){
  return preg_match('@^[-]?[0-9]+$@',trim($input)) === 1;
}

function flash_zoom_options_page() {
		add_options_page('FlashZoom', 'FlashZoom', 8, basename(__FILE__), 'flash_zoom_options_subpanel');
}

function flash_zoom_options_subpanel() {
	global $ol_flash, $flashzoom_settings, $_POST, $wp_rewrite;

	if (current_user_can('activate_plugins')) {
		// Easiest test to see if we have been submitted to
		if(isset($_POST['target_width']) || isset($_POST['target_height'])) {
		  if(!isInteger($_POST['target_width'])||!isInteger($_POST['target_height'])){
		    $ol_flash = "Please input the number!";
		  }else{
			// Now we check the hash, to make sure we are not getting CSRF
			  if(fb_is_hash_valid($_POST['token'])) {
				  if (isset($_POST['target_width'])) {
					  $flashzoom_settings['target_width'] = $_POST['target_width'];
					  update_option('flashzoom_settings',$flashzoom_settings);
					  $ol_flash = "Your settings have been saved.";
				  }
				  if (isset($_POST['target_height'])) {
					  $flashzoom_settings['target_height'] = $_POST['target_height'];
					  update_option('flashzoom_settings',$flashzoom_settings);
					  $ol_flash = "Your settings have been saved.";
				  }
			  } else {
				  // Invalid form hash, possible CSRF attempt
				  $ol_flash = "Security hash missing.";
			  } // endif fb_is_hash_valid
			} //endif isInteger
		} // endif isset(feedburner_url)
	} else {
		$ol_flash = "You don't have enough access rights.";
	}
	if ($ol_flash != '') echo '


' . $ol_flash . '

';

	if (current_user_can('activate_plugins')) {
	  $temp_hash = fb_generate_hash();
		fb_store_hash($temp_hash);
		echo '
';
		echo '
Set Up Flash Zoom Size

';
		echo '






Target Width




Target Height








';
		echo '

';
	} else {
		echo '


Sorry, you are not allowed to access this page.

';
	}

}

The flash_zoom_options_page function create an panel flash_zoom_options_subpanel, and the first part of flash_zoom_options_subpanel will check the parameters and store it into database, the other part will display the form.

We have not use the install step, so we add these two lines .

add_option('flashzoom_settings',$data,'FlashZoom Options');
$flashzoom_settings = get_option('flashzoom_settings');

Last, don’t forget the plugin header,  so the wordpress can recognize the plugin. The full plugin is:

/*
Plugin Name: Flash Zoom
Plugin URI: http://rocksun.cn/flash-zoom/
Description: zoom the flash in homepage.
Version: 0.8
Author: Rock Sun
Author URI: http://rocksun.cn/
*/

add_option('flashzoom_settings',$data,'FlashZoom Options');
$flashzoom_settings = get_option('flashzoom_settings');

function isInteger($input){
  return preg_match('@^[-]?[0-9]+$@',trim($input)) === 1;
}

function flash_zoom_options_page() {
		add_options_page('FlashZoom', 'FlashZoom', 8, basename(__FILE__), 'flash_zoom_options_subpanel');
}

function flash_zoom_options_subpanel() {
	global $ol_flash, $flashzoom_settings, $_POST, $wp_rewrite;

	if (current_user_can('activate_plugins')) {
		// Easiest test to see if we have been submitted to
		if(isset($_POST['target_width']) || isset($_POST['target_height'])) {
		  if(!isInteger($_POST['target_width'])||!isInteger($_POST['target_height'])){
		    $ol_flash = "Please input the number!";
		  }else{
			// Now we check the hash, to make sure we are not getting CSRF
			  if(fb_is_hash_valid($_POST['token'])) {
				  if (isset($_POST['target_width'])) {
					  $flashzoom_settings['target_width'] = $_POST['target_width'];
					  update_option('flashzoom_settings',$flashzoom_settings);
					  $ol_flash = "Your settings have been saved.";
				  }
				  if (isset($_POST['target_height'])) {
					  $flashzoom_settings['target_height'] = $_POST['target_height'];
					  update_option('flashzoom_settings',$flashzoom_settings);
					  $ol_flash = "Your settings have been saved.";
				  }
			  } else {
				  // Invalid form hash, possible CSRF attempt
				  $ol_flash = "Security hash missing.";
			  } // endif fb_is_hash_valid
			} //endif isInteger
		} // endif isset(feedburner_url)
	} else {
		$ol_flash = "You don't have enough access rights.";
	}
	if ($ol_flash != '') echo '


' . $ol_flash . '

';

	if (current_user_can('activate_plugins')) {
	  $temp_hash = fb_generate_hash();
		fb_store_hash($temp_hash);
		echo '
';
		echo '
Set Up Flash Zoom Size

';
		echo '






Target Width




Target Height








';
		echo '

';
	} else {
		echo '


Sorry, you are not allowed to access this page.

';
	}

}

function replaceSize($matches)
{
  global $flashzoom_settings;
  $replaceStr = ' width="'.$flashzoom_settings['target_width'].'" height="'.$flashzoom_settings['target_height'].'" ';
  return $matches[1].$replaceStr.$matches[3].$replaceStr.$matches[5];
}

function filter_shrink($content) {
    global $flashzoom_settings;
    if(is_home()){
      $content = preg_replace_callback(
           '|('.'