Who has implemented several projects already with WordPress probably had experienced that a user doesn't have the rights to upload a specific format.

The Plugin Role Manager allows the uploading of all MIME types. But in my opinion this is not the perfect way, and therefore here is a small code snippet that takes adjusting according to the particular requirement.

All allowed types are found in the whitelist-function wp_check_filetype(), in wp-includes/functions.php.
This function has a filter upload_mimes that can be extended. And there we come in and call the MIME types that we need. In the following example, I allow PHP-, XHTML- and htaccess-files. The options are passed in an array and the assignment is important so that WordPress can also assign an icon, like you see on the screenshot.

function my_upload_mimes() {
	$mime_types = array(
		'php|phps'   => 'text/php',
		'xhtm|xhtml' => 'text/html',
		'htaccess'    => 'text/plain'
	);

	return $mime_types;
}

add_filter( 'upload_mimes', 'my_upload_mimes' );

Mime Types

To obtain a list of all MIME types that can be used, you can check out the following list. The list should only contain type files, which are explicitly required, otherwise the above constants can be used.

$mime_types = array(
'323'     => 'text/h323',
'acx'     => 'application/internet-property-stream',
'ai'      => 'application/postscript',
'aif'     => 'audio/x-aiff',
'aifc'    => 'audio/x-aiff',
'aiff'    => 'audio/x-aiff',
'asf'     => 'video/x-ms-asf',
'asr'     => 'video/x-ms-asf',
'asx'     => 'video/x-ms-asf',
'au'      => 'audio/basic',
'avi'     => 'video/x-msvideo',
'axs'     => 'application/olescript',
'bas'     => 'text/plain',
'bcpio'   => 'application/x-bcpio',
'bin'     => 'application/octet-stream',
'bmp'     => 'image/bmp',
'c'       => 'text/plain',
'cat'     => 'application/vnd.ms-pkiseccat',
'cdf'     => 'application/x-cdf',
'cer'     => 'application/x-x509-ca-cert',
'class'   => 'application/octet-stream',
'clp'     => 'application/x-msclip',
'cmx'     => 'image/x-cmx',
'cod'     => 'image/cis-cod',
'cpio'    => 'application/x-cpio',
'crd'     => 'application/x-mscardfile',
'crl'     => 'application/pkix-crl',
'crt'     => 'application/x-x509-ca-cert',
'csh'     => 'application/x-csh',
'css'     => 'text/css',
'dcr'     => 'application/x-director',
'der'     => 'application/x-x509-ca-cert',
'dir'     => 'application/x-director',
'dll'     => 'application/x-msdownload',
'dms'     => 'application/octet-stream',
'doc'     => 'application/msword',
'dot'     => 'application/msword',
'dvi'     => 'application/x-dvi',
'dxr'     => 'application/x-director',
'eps'     => 'application/postscript',
'etx'     => 'text/x-setext',
'evy'     => 'application/envoy',
'exe'     => 'application/octet-stream',
'fif'     => 'application/fractals',
'flr'     => 'x-world/x-vrml',
'gif'     => 'image/gif',
'gtar'    => 'application/x-gtar',
'gz'      => 'application/x-gzip',
'h'       => 'text/plain',
'hdf'     => 'application/x-hdf',
'hlp'     => 'application/winhlp',
'hqx'     => 'application/mac-binhex40',
'hta'     => 'application/hta',
'htc'     => 'text/x-component',
'htm'     => 'text/html',
'html'    => 'text/html',
'htt'     => 'text/webviewhtml',
'ico'     => 'image/x-icon',
'ief'     => 'image/ief',
'iii'     => 'application/x-iphone',
'ins'     => 'application/x-internet-signup',
'isp'     => 'application/x-internet-signup',
'jfif'    => 'image/pipeg',
'jpe'     => 'image/jpeg',
'jpeg'    => 'image/jpeg',
'jpg'     => 'image/jpeg',
'js'      => 'application/x-javascript',
'latex'   => 'application/x-latex',
'lha'     => 'application/octet-stream',
'lsf'     => 'video/x-la-asf',
'lsx'     => 'video/x-la-asf',
'lzh'     => 'application/octet-stream',
'm13'     => 'application/x-msmediaview',
'm14'     => 'application/x-msmediaview',
'm3u'     => 'audio/x-mpegurl',
'man'     => 'application/x-troff-man',
'mdb'     => 'application/x-msaccess',
'me'      => 'application/x-troff-me',
'mht'     => 'message/rfc822',
'mhtml'   => 'message/rfc822',
'mid'     => 'audio/mid',
'mny'     => 'application/x-msmoney',
'mov'     => 'video/quicktime',
'movie'   => 'video/x-sgi-movie',
'mp2'     => 'video/mpeg',
'mp3'     => 'audio/mpeg',
'mpa'     => 'video/mpeg',
'mpe'     => 'video/mpeg',
'mpeg'    => 'video/mpeg',
'mpg'     => 'video/mpeg',
'mpp'     => 'application/vnd.ms-project',
'mpv2'    => 'video/mpeg',
'ms'      => 'application/x-troff-ms',
'mvb'     => 'application/x-msmediaview',
'nws'     => 'message/rfc822',
'oda'     => 'application/oda',
'p10'     => 'application/pkcs10',
'p12'     => 'application/x-pkcs12',
'p7b'     => 'application/x-pkcs7-certificates',
'p7c'     => 'application/x-pkcs7-mime',
'p7m'     => 'application/x-pkcs7-mime',
'p7r'     => 'application/x-pkcs7-certreqresp',
'p7s'     => 'application/x-pkcs7-signature',
'pbm'     => 'image/x-portable-bitmap',
'pdf'     => 'application/pdf',
'pfx'     => 'application/x-pkcs12',
'pgm'     => 'image/x-portable-graymap',
'pko'     => 'application/ynd.ms-pkipko',
'pma'     => 'application/x-perfmon',
'pmc'     => 'application/x-perfmon',
'pml'     => 'application/x-perfmon',
'pmr'     => 'application/x-perfmon',
'pmw'     => 'application/x-perfmon',
'pnm'     => 'image/x-portable-anymap',
'pot'     => 'application/vnd.ms-powerpoint',
'ppm'     => 'image/x-portable-pixmap',
'pps'     => 'application/vnd.ms-powerpoint',
'ppt'     => 'application/vnd.ms-powerpoint',
'prf'     => 'application/pics-rules',
'ps'      => 'application/postscript',
'pub'     => 'application/x-mspublisher',
'qt'      => 'video/quicktime',
'ra'      => 'audio/x-pn-realaudio',
'ram'     => 'audio/x-pn-realaudio',
'ras'     => 'image/x-cmu-raster',
'rgb'     => 'image/x-rgb',
'rmi'     => 'audio/mid',
'roff'    => 'application/x-troff',
'rtf'     => 'application/rtf',
'rtx'     => 'text/richtext',
'scd'     => 'application/x-msschedule',
'sct'     => 'text/scriptlet',
'setpay'  => 'application/set-payment-initiation',
'setreg'  => 'application/set-registration-initiation',
'sh'      => 'application/x-sh',
'shar'    => 'application/x-shar',
'sit'     => 'application/x-stuffit',
'snd'     => 'audio/basic',
'spc'     => 'application/x-pkcs7-certificates',
'spl'     => 'application/futuresplash',
'src'     => 'application/x-wais-source',
'sst'     => 'application/vnd.ms-pkicertstore',
'stl'     => 'application/vnd.ms-pkistl',
'stm'     => 'text/html',
'svg'     => 'image/svg+xml',
'sv4cpio' => 'application/x-sv4cpio',
'sv4crc'  => 'application/x-sv4crc',
't'       => 'application/x-troff',
'tar'     => 'application/x-tar',
'tcl'     => 'application/x-tcl',
'tex'     => 'application/x-tex',
'texi'    => 'application/x-texinfo',
'texinfo' => 'application/x-texinfo',
'tgz'     => 'application/x-compressed',
'tif'     => 'image/tiff',
'tiff'    => 'image/tiff',
'tr'      => 'application/x-troff',
'trm'     => 'application/x-msterminal',
'tsv'     => 'text/tab-separated-values',
'txt'     => 'text/plain',
'uls'     => 'text/iuls',
'ustar'   => 'application/x-ustar',
'vcf'     => 'text/x-vcard',
'vrml'    => 'x-world/x-vrml',
'wav'     => 'audio/x-wav',
'wcm'     => 'application/vnd.ms-works',
'wdb'     => 'application/vnd.ms-works',
'wks'     => 'application/vnd.ms-works',
'wmf'     => 'application/x-msmetafile',
'wps'     => 'application/vnd.ms-works',
'wri'     => 'application/x-mswrite',
'wrl'     => 'x-world/x-vrml',
'wrz'     => 'x-world/x-vrml',
'xaf'     => 'x-world/x-vrml',
'xbm'     => 'image/x-xbitmap',
'xla'     => 'application/vnd.ms-excel',
'xlc'     => 'application/vnd.ms-excel',
'xlm'     => 'application/vnd.ms-excel',
'xls'     => 'application/vnd.ms-excel',
'xlt'     => 'application/vnd.ms-excel',
'xlw'     => 'application/vnd.ms-excel',
'xof'     => 'x-world/x-vrml',
'xpm'     => 'image/x-xpixmap',
'xwd'     => 'image/x-xwindowdump',
'z'       => 'application/x-compress',
'zip'     => 'application/zip'
);

Function remove_action

remove_action( $tag, $function_to_add, $priority, $accepted_args );

This function removes a function attached to a specified action hook. This method can be used to remove default functions attached to a specific action hook and possibly replace them with a substitute.

Important: To remove a hook, the $function_to_remove and $priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.
via: WP Codexy

The following syntax shows an excerpt, only a part of the output you can have in your theme. They result from the standard functions, which are loaded in the head of the theme. Visible, if you search in the file wp-includes/default-filters.php for the Hook wp_head. Not all filters should be deactivated, because in most cases they are useful. But WordPress is not only as classical blog in use and therefore some functions are not necessary.

<link rel="alternate" type="application/rss+xml" title="WP Engineer RSS Feed" href="http://wpengineer.com/feed/" />
<link rel="alternate" type="application/atom+xml" title="WP Engineer Atom Feed" href="http://wpengineer.com/feed/atom/" />
<link rel="pingback" href="http://wpengineer.com/blog/xmlrpc.php" />
<link rel="EditURI" type="application/rsd+xml" title="RSD" href="http://wpengineer.com/xmlrpc.php?rsd" />
<link rel='index' title='WP Engineer' href='http://wpengineer.com' />
<link rel='start' title='Use WordPress 2.7 Offline' href='http://wpengineer.com/use-wordpress-27-offline/' />
<link rel='prev' title='Recents Drafts All Authors' href='http://wpengineer.com/recents-drafts-all-authors/' />

This is an example, not a recommendation where some functions are deactivated. Check your header and turn off what you don't need. Less markup and better loading time.

remove_action( 'wp_head', 'feed_links_extra', 3 ); // Display the links to the extra feeds such as category feeds
remove_action( 'wp_head', 'feed_links', 2 ); // Display the links to the general feeds: Post and Comment Feed
remove_action( 'wp_head', 'rsd_link' ); // Display the link to the Really Simple Discovery service endpoint, EditURI link
remove_action( 'wp_head', 'wlwmanifest_link' ); // Display the link to the Windows Live Writer manifest file.
remove_action( 'wp_head', 'index_rel_link' ); // index link
remove_action( 'wp_head', 'parent_post_rel_link', 10, 0 ); // prev link
remove_action( 'wp_head', 'start_post_rel_link', 10, 0 ); // start link
remove_action( 'wp_head', 'adjacent_posts_rel_link', 10, 0 ); // Display relational links for the posts adjacent to the current post.
remove_action( 'wp_head', 'wp_generator' ); // Display the XHTML generator that is generated on the wp_head hook, WP version

But also to use the memory, it requires a small syntax extension in the configuration of WordPress.

To have a quick overview about the demand: Use the Plugin for WordPress WP-Memory-Usage by Alex Rabe ...

... or the more extensive version of an analysis with the Plugin WordPress System Health by Heiko Rabe.

More Information

Thus, it provides the analysis of blogs and a quick way to see the problems at a customers blog or project of your own. This WordPress Plugin Health System will not only provide information on the status of WordPress, but will also provide information on important configuration settings, supply information on the state of the database and also the tables and information about PHP. In each mode you can add various details, which provide a lot of information to the WordPress experts about the system without the need to investigate the individual Settings, the PHP and the database information.

More Memory

It is recommended when working with WordPress to increase memory, as long the host permits. This requires the expansion of wp-config.php; the best way is to do it in steps in order to check the possibilities of the host.

// more memory
define('WP_MEMORY_LIMIT', '64M');
// even more memory
define('WP_MEMORY_LIMIT', '96M');
// a good deal more memory 
define('WP_MEMORY_LIMIT', '128M');

Will you get a white page as return, then it was too much and it goes back down to 32 MByte. Good luck.

This problem in 2.8 continues to be an issue in various installations. Who wants to change the value should set it to 1, and should no longer have problems. All other users can only hope that it will be changed in 2.8.1.

Original code in WordPress 2.8

$cron_url = get_option( 'siteurl' ) . '/wp-cron.php?doing_wp_cron';
wp_remote_post( $cron_url, array('timeout' => 0.01, 'blocking' => false, 'sslverify' => apply_filters('https_local_ssl_verify', true)) );

after change the value

$cron_url = get_option( 'siteurl' ) . '/wp-cron.php?doing_wp_cron';
wp_remote_post( $cron_url, array('timeout' => 1, 'blocking' => false, 'sslverify' => apply_filters('https_local_ssl_verify', true)) );

/**
 * @version WP 2.7
 * Add action link(s) to plugins page
 */
function set_plugin_meta27($links) {

	$plugin = plugin_basename(__FILE__);

	$settings_link = sprintf( '<a href="options-general.php?page=%s">%s</a>', $plugin, __('Settings') );
	array_unshift( $links, $settings_link );

	return $links;
}

add_filter( 'plugin_action_links_' . $plugin, 'set_plugin_meta27' );

Since version 2.8 the backend is a little bit different, also the meta links to Plugins are displayed differently from now on, which you can use as you can see on this screenshot.

You can use following code to set the link to your options page. You can use the term „Settings“ , so you don't have to take care about other languages, since it is already in the respective language package included. The word will be adjust automatically to the according language.

function set_plugin_meta($links, $file) {

	$plugin = plugin_basename(__FILE__);

	// create link
	if ($file == $plugin) {
		return array_merge(
			$links,
			array( sprintf( '<a href="options-general.php?page=%s">%s</a>', $plugin, __('Settings') ) )
		);
	}

	return $links;
}

add_filter( 'plugin_row_meta', 'set_plugin_meta', 10, 2 );

Alternativ you can use the follow functions to link before other links on the plugin page.

// plugin definitions
define( 'FB_BASENAME', plugin_basename( __FILE__ ) );
define( 'FB_BASEFOLDER', plugin_basename( dirname( __FILE__ ) ) );
define( 'FB_FILENAME', str_replace( FB_BASEFOLDER.'/', '', plugin_basename(__FILE__) ) );

function filter_plugin_meta($links, $file) {

	/* create link */
	if ( $file == FB_BASENAME ) {
		array_unshift(
			$links,
			sprintf( '<a href="options-general.php?page=%s">%s</a>', FB_FILENAME, __('Settings') )
		);
	}

	return $links;
}

global $wp_version;
if ( version_compare( $wp_version, '2.8alpha', '>' ) )
	add_filter( 'plugin_row_meta', 'filter_plugin_meta', 10, 2 ); // only 2.8 and higher
add_filter( 'plugin_action_links', 'filter_plugin_meta', 10, 2 );

This little hack is easy to do but has a significant value for the user, since it's easy to get to the options page. It's just sad, that the developer of WordPress always changing the hook, so you have to adjust it after every new version. Hope that won't happen again in the near future.

Until WordPress 2.7

Up to this version of WordPress it works only with an adjustment in the core, in wp-includes/class-snoopy.php. Here you have to change the settings of $proxy_host, $proxy_port and $_isproxy. The value of var $_isproxy = false; will of course have TRUE as value.

var $host       = "www.php.net"; // host name we are connecting to
var $port       = 8080; // port we are connecting to
var $proxy_host = ""; // proxy host to use
var $proxy_port = ""; // proxy port to use
var $proxy_user = ""; // proxy user to use
var $proxy_pass = ""; // proxy password to use
var $_isproxy   = true; // set if using a proxy server

WordPress 2.8

With the new version it is much easier, because no more intrusion into the core files is necessary and the possibility to define the values in the configuration file wp-config.php.

define('WP_PROXY_HOST', '192.168.84.101');
define('WP_PROXY_PORT', '8080');
define('WP_PROXY_USERNAME', 'my_user_name');
define('WP_PROXY_PASSWORD', 'my_password');
define('WP_PROXY_BYPASS_HOSTS', 'localhost, www.example.com');

Various references are also inTicket 4011.

As of WordPress version 2.8 the function can take two parameters:

/**
 * @param string $path Optional. Path relative to the plugins url.
 * @param string $plugin Optional. The plugin file that you want to be relative to - i.e. pass in __FILE__
 * @return string Plugins url link with optional path appended.
*/
function plugins_url($path = '', $plugin = '')

So far only the $ path parameter could be passed, so that required a proper definition of the folder.

$style = plugins_url( 'my_plugin_folder/css/style-frontend.css' );

With the extension in version 2.8 of WordPress it can be done like:

$style = plugins_url( 'css/style-frontend.css', __FILE__ );

The use should make it simpler and clearer. But the question will come up, how do I do backwards compatibility of the plugin? You can either use the version query:

if ( version_compare( $wp_version, '2.8dev', '>' ) )

and then supplement or write a custom function for the replacement:

// function for WP < 2.8
function plugins_url($path = '', $plugin = '') {
  if ( function_exists('is_ssl') )
    $scheme = ( is_ssl() ? 'https' : 'http' );
  else
    $scheme = 'http';
  $url = WP_PLUGIN_URL;
  if ( 0 === strpos($url, 'http') ) {
    if ( function_exists('is_ssl') && is_ssl() )
      $url = str_replace( 'http://', "{$scheme}://", $url );
  }

  if ( !empty($plugin) && is_string($plugin) )
  {
    $folder = dirname(plugin_basename($plugin));
    if ('.' != $folder)
      $url .= '/' . ltrim($folder, '/');
  }

  if ( !empty($path) && is_string($path) && strpos($path, '..') === false )
    $url .= '/' . ltrim($path, '/');

  return apply_filters('plugins_url', $url, $path, $plugin);
}

This is only an alternative, the possibilities are endless - maybe one or the other has a beautiful idea and solution?

The favorites are changing from 2.8 in dependence of the page that you are using. I hope the screenshot shows it.

Also the Plugin page was revised. From version 2.8 on, WordPress saves user behaviors and hence you are always in the area that you used the last time - definitely an added value.
This applies also for the comment administration. In addition, the Plugin page has changed completely, so that you get an own summary on various topics.

• New Template Tag: the_modified_author()
  In the use of different authors long awaited, in 2.8 available
• Widget API
  Widgets have been loved by most users and tolerated by developers. The new API will simplify it and the access to the class makes this possible. This means that multiple instances now finally possible.
• Optimized loading of JavaScript
  Since 2.7 is clean and checked loading of JS involved. Additional functions provide a control of the loading process and dependency. Now, via WordPress, scripts are going to summarized and returned in a single call. You can also include scripts in the footer now, directly through the targeted functions.
• More options, when making the frontend, with the new Template Tag body_class()
• SimplePie in Core
  With version 2.8 Magpie is removed and the well-known SimplePie project comes into the core; in my view in relation to use of feeds, especially in the ATOM standard, a lot more comfortable.

What are your most exciting innovations in 2.8?