includes/Html.php

   1 <?php
   2 /**
   3  * Collection of methods to generate HTML content
   4  *
   5  * Copyright © 2009 Aryeh Gregor
   6  * http://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  */
  25
  26 /**
  27  * This class is a collection of static functions that serve two purposes:
  28  *
  29  * 1) Implement any algorithms specified by HTML5, or other HTML
  30  * specifications, in a convenient and self-contained way.
  31  *
  32  * 2) Allow HTML elements to be conveniently and safely generated, like the
  33  * current Xml class but a) less confused (Xml supports HTML-specific things,
  34  * but only sometimes!) and b) not necessarily confined to XML-compatible
  35  * output.
  36  *
  37  * There are two important configuration options this class uses:
  38  *
  39  * $wgHtml5: If this is set to false, then all output should be valid XHTML 1.0
  40  *     Transitional.
  41  * $wgWellFormedXml: If this is set to true, then all output should be
  42  *     well-formed XML (quotes on attributes, self-closing tags, etc.).
  43  *
  44  * This class is meant to be confined to utility functions that are called from
  45  * trusted code paths.  It does not do enforcement of policy like not allowing
  46  * <a> elements.
  47  *
  48  * @since 1.16
  49  */
  50 class Html {
  51         # List of void elements from HTML5, section 9.1.2 as of 2009-08-10
  52         private static $voidElements = array(
  53                 'area',
  54                 'base',
  55                 'br',
  56                 'col',
  57                 'command',
  58                 'embed',
  59                 'hr',
  60                 'img',
  61                 'input',
  62                 'keygen',
  63                 'link',
  64                 'meta',
  65                 'param',
  66                 'source',
  67         );
  68
  69         # Boolean attributes, which may have the value omitted entirely.  Manually
  70         # collected from the HTML5 spec as of 2010-06-07.
  71         private static $boolAttribs = array(
  72                 'async',
  73                 'autofocus',
  74                 'autoplay',
  75                 'checked',
  76                 'controls',
  77                 'defer',
  78                 'disabled',
  79                 'formnovalidate',
  80                 'hidden',
  81                 'ismap',
  82                 'itemscope',
  83                 'loop',
  84                 'multiple',
  85                 'novalidate',
  86                 'open',
  87                 'pubdate',
  88                 'readonly',
  89                 'required',
  90                 'reversed',
  91                 'scoped',
  92                 'seamless',
  93                 'selected',
  94         );
  95
  96         /**
  97          * Returns an HTML element in a string.  The major advantage here over
  98          * manually typing out the HTML is that it will escape all attribute
  99          * values.  If you're hardcoding all the attributes, or there are none, you
 100          * should probably type out the string yourself.
 101          *
 102          * This is quite similar to Xml::tags(), but it implements some useful
 103          * HTML-specific logic.  For instance, there is no $allowShortTag
 104          * parameter: the closing tag is magically omitted if $element has an empty
 105          * content model.  If $wgWellFormedXml is false, then a few bytes will be
 106          * shaved off the HTML output as well.  In the future, other HTML-specific
 107          * features might be added, like allowing arrays for the values of
 108          * attributes like class= and media=.
 109          *
 110          * @param $element string The element's name, e.g., 'a'
 111          * @param $attribs array  Associative array of attributes, e.g., array(
 112          *   'href' => 'http://www.mediawiki.org/' ).  See expandAttributes() for
 113          *   further documentation.
 114          * @param $contents string The raw HTML contents of the element: *not*
 115          *   escaped!
 116          * @return string Raw HTML
 117          */
 118         public static function rawElement( $element, $attribs = array(), $contents = '' ) {
 119                 global $wgWellFormedXml;
 120                 $start = self::openElement( $element, $attribs );
 121                 if ( in_array( $element, self::$voidElements ) ) {
 122                         if ( $wgWellFormedXml ) {
 123                                 # Silly XML.
 124                                 return substr( $start, 0, -1 ) . ' />';
 125                         }
 126                         return $start;
 127                 } else {
 128                         return "$start$contents" . self::closeElement( $element );
 129                 }
 130         }
 131
 132         /**
 133          * Identical to rawElement(), but HTML-escapes $contents (like
 134          * Xml::element()).
 135          *
 136          * @param $element string
 137          * @param $attribs array
 138          * @param $contents string
 139          *
 140          * @return string
 141          */
 142         public static function element( $element, $attribs = array(), $contents = '' ) {
 143                 return self::rawElement( $element, $attribs, strtr( $contents, array(
 144                         # There's no point in escaping quotes, >, etc. in the contents of
 145                         # elements.
 146                         '&' => '&amp;',
 147                         '<' => '&lt;'
 148                 ) ) );
 149         }
 150
 151         /**
 152          * Identical to rawElement(), but has no third parameter and omits the end
 153          * tag (and the self-closing '/' in XML mode for empty elements).
 154          *
 155          * @param $element string
 156          * @param $attribs array
 157          *
 158          * @return string
 159          */
 160         public static function openElement( $element, $attribs = array() ) {
 161                 global $wgHtml5, $wgWellFormedXml;
 162                 $attribs = (array)$attribs;
 163                 # This is not required in HTML5, but let's do it anyway, for
 164                 # consistency and better compression.
 165                 $element = strtolower( $element );
 166
 167                 # In text/html, initial <html> and <head> tags can be omitted under
 168                 # pretty much any sane circumstances, if they have no attributes.  See:
 169                 # <http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#optional-tags>
 170                 if ( !$wgWellFormedXml && !$attribs
 171                 && in_array( $element, array( 'html', 'head' ) ) ) {
 172                         return '';
 173                 }
 174
 175                 # Remove HTML5-only attributes if we aren't doing HTML5, and disable
 176                 # form validation regardless (see bug 23769 and the more detailed
 177                 # comment in expandAttributes())
 178                 if ( $element == 'input' ) {
 179                         # Whitelist of types that don't cause validation.  All except
 180                         # 'search' are valid in XHTML1.
 181                         $validTypes = array(
 182                                 'hidden',
 183                                 'text',
 184                                 'password',
 185                                 'checkbox',
 186                                 'radio',
 187                                 'file',
 188                                 'submit',
 189                                 'image',
 190                                 'reset',
 191                                 'button',
 192                                 'search',
 193                         );
 194                         if ( isset( $attribs['type'] )
 195                         && !in_array( $attribs['type'], $validTypes ) ) {
 196                                 unset( $attribs['type'] );
 197                         }
 198                         if ( isset( $attribs['type'] ) && $attribs['type'] == 'search'
 199                         && !$wgHtml5 ) {
 200                                 unset( $attribs['type'] );
 201                         }
 202                 }
 203                 if ( !$wgHtml5 && $element == 'textarea' && isset( $attribs['maxlength'] ) ) {
 204                         unset( $attribs['maxlength'] );
 205                 }
 206
 207                 return "<$element" . self::expandAttributes(
 208                         self::dropDefaults( $element, $attribs ) ) . '>';
 209         }
 210
 211         /**
 212          * Returns "</$element>", except if $wgWellFormedXml is off, in which case
 213          * it returns the empty string when that's guaranteed to be safe.
 214          *
 215          * @since 1.17
 216          * @param $element string Name of the element, e.g., 'a'
 217          * @return string A closing tag, if required
 218          */
 219         public static function closeElement( $element ) {
 220                 global $wgWellFormedXml;
 221
 222                 $element = strtolower( $element );
 223
 224                 # Reference:
 225                 # http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#optional-tags
 226                 if ( !$wgWellFormedXml && in_array( $element, array(
 227                         'html',
 228                         'head',
 229                         'body',
 230                         'li',
 231                         'dt',
 232                         'dd',
 233                         'tr',
 234                         'td',
 235                         'th',
 236                 ) ) ) {
 237                         return '';
 238                 }
 239                 return "</$element>";
 240         }
 241
 242         /**
 243          * Given an element name and an associative array of element attributes,
 244          * return an array that is functionally identical to the input array, but
 245          * possibly smaller.  In particular, attributes might be stripped if they
 246          * are given their default values.
 247          *
 248          * This method is not guaranteed to remove all redundant attributes, only
 249          * some common ones and some others selected arbitrarily at random.  It
 250          * only guarantees that the output array should be functionally identical
 251          * to the input array (currently per the HTML 5 draft as of 2009-09-06).
 252          *
 253          * @param $element string Name of the element, e.g., 'a'
 254          * @param $attribs array  Associative array of attributes, e.g., array(
 255          *   'href' => 'http://www.mediawiki.org/' ).  See expandAttributes() for
 256          *   further documentation.
 257          * @return array An array of attributes functionally identical to $attribs
 258          */
 259         private static function dropDefaults( $element, $attribs ) {
 260                 # Don't bother doing anything if we aren't outputting HTML5; it's too
 261                 # much of a pain to maintain two sets of defaults.
 262                 global $wgHtml5;
 263                 if ( !$wgHtml5 ) {
 264                         return $attribs;
 265                 }
 266
 267                 static $attribDefaults = array(
 268                         'area' => array( 'shape' => 'rect' ),
 269                         'button' => array(
 270                                 'formaction' => 'GET',
 271                                 'formenctype' => 'application/x-www-form-urlencoded',
 272                                 'type' => 'submit',
 273                         ),
 274                         'canvas' => array(
 275                                 'height' => '150',
 276                                 'width' => '300',
 277                         ),
 278                         'command' => array( 'type' => 'command' ),
 279                         'form' => array(
 280                                 'action' => 'GET',
 281                                 'autocomplete' => 'on',
 282                                 'enctype' => 'application/x-www-form-urlencoded',
 283                         ),
 284                         'input' => array(
 285                                 'formaction' => 'GET',
 286                                 'type' => 'text',
 287                                 'value' => '',
 288                         ),
 289                         'keygen' => array( 'keytype' => 'rsa' ),
 290                         'link' => array( 'media' => 'all' ),
 291                         'menu' => array( 'type' => 'list' ),
 292                         # Note: the use of text/javascript here instead of other JavaScript
 293                         # MIME types follows the HTML5 spec.
 294                         'script' => array( 'type' => 'text/javascript' ),
 295                         'style' => array(
 296                                 'media' => 'all',
 297                                 'type' => 'text/css',
 298                         ),
 299                         'textarea' => array( 'wrap' => 'soft' ),
 300                 );
 301
 302                 $element = strtolower( $element );
 303
 304                 foreach ( $attribs as $attrib => $value ) {
 305                         $lcattrib = strtolower( $attrib );
 306                         $value = strval( $value );
 307
 308                         # Simple checks using $attribDefaults
 309                         if ( isset( $attribDefaults[$element][$lcattrib] ) &&
 310                         $attribDefaults[$element][$lcattrib] == $value ) {
 311                                 unset( $attribs[$attrib] );
 312                         }
 313
 314                         if ( $lcattrib == 'class' && $value == '' ) {
 315                                 unset( $attribs[$attrib] );
 316                         }
 317                 }
 318
 319                 # More subtle checks
 320                 if ( $element === 'link' && isset( $attribs['type'] )
 321                 && strval( $attribs['type'] ) == 'text/css' ) {
 322                         unset( $attribs['type'] );
 323                 }
 324                 if ( $element === 'select' && isset( $attribs['size'] ) ) {
 325                         if ( in_array( 'multiple', $attribs )
 326                                 || ( isset( $attribs['multiple'] ) && $attribs['multiple'] !== false )
 327                         ) {
 328                                 # A multi-select
 329                                 if ( strval( $attribs['size'] ) == '4' ) {
 330                                         unset( $attribs['size'] );
 331                                 }
 332                         } else {
 333                                 # Single select
 334                                 if ( strval( $attribs['size'] ) == '1' ) {
 335                                         unset( $attribs['size'] );
 336                                 }
 337                         }
 338                 }
 339
 340                 return $attribs;
 341         }
 342
 343         /**
 344          * Given an associative array of element attributes, generate a string
 345          * to stick after the element name in HTML output.  Like array( 'href' =>
 346          * 'http://www.mediawiki.org/' ) becomes something like
 347          * ' href="http://www.mediawiki.org"'.  Again, this is like
 348          * Xml::expandAttributes(), but it implements some HTML-specific logic.
 349          * For instance, it will omit quotation marks if $wgWellFormedXml is false,
 350          * and will treat boolean attributes specially.
 351          *
 352          * @param $attribs array Associative array of attributes, e.g., array(
 353          *   'href' => 'http://www.mediawiki.org/' ).  Values will be HTML-escaped.
 354          *   A value of false means to omit the attribute.  For boolean attributes,
 355          *   you can omit the key, e.g., array( 'checked' ) instead of
 356          *   array( 'checked' => 'checked' ) or such.
 357          * @return string HTML fragment that goes between element name and '>'
 358          *   (starting with a space if at least one attribute is output)
 359          */
 360         public static function expandAttributes( $attribs ) {
 361                 global $wgHtml5, $wgWellFormedXml;
 362
 363                 $ret = '';
 364                 $attribs = (array)$attribs;
 365                 foreach ( $attribs as $key => $value ) {
 366                         if ( $value === false || is_null( $value ) ) {
 367                                 continue;
 368                         }
 369
 370                         # For boolean attributes, support array( 'foo' ) instead of
 371                         # requiring array( 'foo' => 'meaningless' ).
 372                         if ( is_int( $key )
 373                         && in_array( strtolower( $value ), self::$boolAttribs ) ) {
 374                                 $key = $value;
 375                         }
 376
 377                         # Not technically required in HTML5, but required in XHTML 1.0,
 378                         # and we'd like consistency and better compression anyway.
 379                         $key = strtolower( $key );
 380
 381                         # Bug 23769: Blacklist all form validation attributes for now.  Current
 382                         # (June 2010) WebKit has no UI, so the form just refuses to submit
 383                         # without telling the user why, which is much worse than failing
 384                         # server-side validation.  Opera is the only other implementation at
 385                         # this time, and has ugly UI, so just kill the feature entirely until
 386                         # we have at least one good implementation.
 387                         if ( in_array( $key, array( 'max', 'min', 'pattern', 'required', 'step' ) ) ) {
 388                                 continue;
 389                         }
 390
 391                         # Here we're blacklisting some HTML5-only attributes...
 392                         if ( !$wgHtml5 && in_array( $key, array(
 393                                         'autocomplete',
 394                                         'autofocus',
 395                                         'max',
 396                                         'min',
 397                                         'multiple',
 398                                         'pattern',
 399                                         'placeholder',
 400                                         'required',
 401                                         'step',
 402                                         'spellcheck',
 403                         ) ) ) {
 404                                 continue;
 405                         }
 406
 407                         # See the "Attributes" section in the HTML syntax part of HTML5,
 408                         # 9.1.2.3 as of 2009-08-10.  Most attributes can have quotation
 409                         # marks omitted, but not all.  (Although a literal " is not
 410                         # permitted, we don't check for that, since it will be escaped
 411                         # anyway.)
 412                         #
 413                         # See also research done on further characters that need to be
 414                         # escaped: http://code.google.com/p/html5lib/issues/detail?id=93
 415                         $badChars = "\\x00- '=<>`/\x{00a0}\x{1680}\x{180e}\x{180F}\x{2000}\x{2001}"
 416                                 . "\x{2002}\x{2003}\x{2004}\x{2005}\x{2006}\x{2007}\x{2008}\x{2009}"
 417                                 . "\x{200A}\x{2028}\x{2029}\x{202F}\x{205F}\x{3000}";
 418                         if ( $wgWellFormedXml || $value === ''
 419                         || preg_match( "![$badChars]!u", $value ) ) {
 420                                 $quote = '"';
 421                         } else {
 422                                 $quote = '';
 423                         }
 424
 425                         if ( in_array( $key, self::$boolAttribs ) ) {
 426                                 # In XHTML 1.0 Transitional, the value needs to be equal to the
 427                                 # key.  In HTML5, we can leave the value empty instead.  If we
 428                                 # don't need well-formed XML, we can omit the = entirely.
 429                                 if ( !$wgWellFormedXml ) {
 430                                         $ret .= " $key";
 431                                 } elseif ( $wgHtml5 ) {
 432                                         $ret .= " $key=\"\"";
 433                                 } else {
 434                                         $ret .= " $key=\"$key\"";
 435                                 }
 436                         } else {
 437                                 # Apparently we need to entity-encode \n, \r, \t, although the
 438                                 # spec doesn't mention that.  Since we're doing strtr() anyway,
 439                                 # and we don't need <> escaped here, we may as well not call
 440                                 # htmlspecialchars().  FIXME: verify that we actually need to
 441                                 # escape \n\r\t here, and explain why, exactly.
 442                                 #
 443                                 # We could call Sanitizer::encodeAttribute() for this, but we
 444                                 # don't because we're stubborn and like our marginal savings on
 445                                 # byte size from not having to encode unnecessary quotes.
 446                                 $map = array(
 447                                         '&' => '&amp;',
 448                                         '"' => '&quot;',
 449                                         "\n" => '&#10;',
 450                                         "\r" => '&#13;',
 451                                         "\t" => '&#9;'
 452                                 );
 453                                 if ( $wgWellFormedXml ) {
 454                                         # This is allowed per spec: <http://www.w3.org/TR/xml/#NT-AttValue>
 455                                         # But reportedly it breaks some XML tools?  FIXME: is this
 456                                         # really true?
 457                                         $map['<'] = '&lt;';
 458                                 }
 459                                 $ret .= " $key=$quote" . strtr( $value, $map ) . $quote;
 460                         }
 461                 }
 462                 return $ret;
 463         }
 464
 465         /**
 466          * Output a <script> tag with the given contents.  TODO: do some useful
 467          * escaping as well, like if $contents contains literal '</script>' or (for
 468          * XML) literal "]]>".
 469          *
 470          * @param $contents string JavaScript
 471          * @return string Raw HTML
 472          */
 473         public static function inlineScript( $contents ) {
 474                 global $wgHtml5, $wgJsMimeType, $wgWellFormedXml;
 475
 476                 $attrs = array();
 477                 if ( !$wgHtml5 ) {
 478                         $attrs['type'] = $wgJsMimeType;
 479                 }
 480                 if ( $wgWellFormedXml && preg_match( '/[<&]/', $contents ) ) {
 481                         $contents = "/*<![CDATA[*/$contents/*]]>*/";
 482                 }
 483                 return self::rawElement( 'script', $attrs, $contents );
 484         }
 485
 486         /**
 487          * Output a <script> tag linking to the given URL, e.g.,
 488          * <script src=foo.js></script>.
 489          *
 490          * @param $url string
 491          * @return string Raw HTML
 492          */
 493         public static function linkedScript( $url ) {
 494                 global $wgHtml5, $wgJsMimeType;
 495
 496                 $attrs = array( 'src' => $url );
 497                 if ( !$wgHtml5 ) {
 498                         $attrs['type'] = $wgJsMimeType;
 499                 }
 500                 return self::element( 'script', $attrs );
 501         }
 502
 503         /**
 504          * Output a <style> tag with the given contents for the given media type
 505          * (if any).  TODO: do some useful escaping as well, like if $contents
 506          * contains literal '</style>' (admittedly unlikely).
 507          *
 508          * @param $contents string CSS
 509          * @param $media mixed A media type string, like 'screen'
 510          * @return string Raw HTML
 511          */
 512         public static function inlineStyle( $contents, $media = 'all' ) {
 513                 global $wgWellFormedXml;
 514
 515                 if ( $wgWellFormedXml && preg_match( '/[<&]/', $contents ) ) {
 516                         $contents = "/*<![CDATA[*/$contents/*]]>*/";
 517                 }
 518                 return self::rawElement( 'style', array(
 519                         'type' => 'text/css',
 520                         'media' => $media,
 521                 ), $contents );
 522         }
 523
 524         /**
 525          * Output a <link rel=stylesheet> linking to the given URL for the given
 526          * media type (if any).
 527          *
 528          * @param $url string
 529          * @param $media mixed A media type string, like 'screen'
 530          * @return string Raw HTML
 531          */
 532         public static function linkedStyle( $url, $media = 'all' ) {
 533                 return self::element( 'link', array(
 534                         'rel' => 'stylesheet',
 535                         'href' => $url,
 536                         'type' => 'text/css',
 537                         'media' => $media,
 538                 ) );
 539         }
 540
 541         /**
 542          * Convenience function to produce an <input> element.  This supports the
 543          * new HTML5 input types and attributes, and will silently strip them if
 544          * $wgHtml5 is false.
 545          *
 546          * @param $name    string name attribute
 547          * @param $value   mixed  value attribute
 548          * @param $type    string type attribute
 549          * @param $attribs array  Associative array of miscellaneous extra
 550          *   attributes, passed to Html::element()
 551          * @return string Raw HTML
 552          */
 553         public static function input( $name, $value = '', $type = 'text', $attribs = array() ) {
 554                 $attribs['type'] = $type;
 555                 $attribs['value'] = $value;
 556                 $attribs['name'] = $name;
 557
 558                 return self::element( 'input', $attribs );
 559         }
 560
 561         /**
 562          * Convenience function to produce an input element with type=hidden
 563          *
 564          * @param $name    string name attribute
 565          * @param $value   string value attribute
 566          * @param $attribs array  Associative array of miscellaneous extra
 567          *   attributes, passed to Html::element()
 568          * @return string Raw HTML
 569          */
 570         public static function hidden( $name, $value, $attribs = array() ) {
 571                 return self::input( $name, $value, 'hidden', $attribs );
 572         }
 573
 574         /**
 575          * Convenience function to produce an <input> element.  This supports leaving
 576          * out the cols= and rows= which Xml requires and are required by HTML4/XHTML
 577          * but not required by HTML5 and will silently set cols="" and rows="" if
 578          * $wgHtml5 is false and cols and rows are omitted (HTML4 validates present
 579          * but empty cols="" and rows="" as valid).
 580          *
 581          * @param $name    string name attribute
 582          * @param $value   string value attribute
 583          * @param $attribs array  Associative array of miscellaneous extra
 584          *   attributes, passed to Html::element()
 585          * @return string Raw HTML
 586          */
 587         public static function textarea( $name, $value = '', $attribs = array() ) {
 588                 global $wgHtml5;
 589                 $attribs['name'] = $name;
 590                 if ( !$wgHtml5 ) {
 591                         if ( !isset( $attribs['cols'] ) ) {
 592                                 $attribs['cols'] = "";
 593                         }
 594                         if ( !isset( $attribs['rows'] ) ) {
 595                                 $attribs['rows'] = "";
 596                         }
 597                 }
 598                 return self::element( 'textarea', $attribs, $value );
 599         }
 600
 601         /**
 602          * Constructs the opening html-tag with necessary doctypes depending on
 603          * global variables.
 604          *
 605          * @param $attribs array  Associative array of miscellaneous extra
 606          *   attributes, passed to Html::element() of html tag.
 607          * @return string  Raw HTML
 608          */
 609         public static function htmlHeader( $attribs = array() ) {
 610                 $ret = '';
 611
 612                 global $wgMimeType;
 613                 if ( self::isXmlMimeType( $wgMimeType ) ) {
 614                         $ret .= "<?xml version=\"1.0\" encoding=\"UTF-8\" ?" . ">\n";
 615                 }
 616
 617                 global $wgHtml5, $wgHtml5Version, $wgDocType, $wgDTD;
 618                 global $wgXhtmlNamespaces, $wgXhtmlDefaultNamespace;
 619                 if ( $wgHtml5 ) {
 620                         $ret .= "<!DOCTYPE html>\n";
 621                         if ( $wgHtml5Version ) {
 622                                 $attribs['version'] = $wgHtml5Version;
 623                         }
 624                 } else {
 625                         $ret .= "<!DOCTYPE html PUBLIC \"$wgDocType\" \"$wgDTD\">\n";
 626                         $attribs['xmlns'] = $wgXhtmlDefaultNamespace;
 627                         foreach ( $wgXhtmlNamespaces as $tag => $ns ) {
 628                                 $attribs["xmlns:$tag"] = $ns;
 629                         }
 630                 }
 631                 $html = Html::openElement( 'html', $attribs );
 632                 if ( $html ) {
 633                         $html .= "\n";
 634                 }
 635                 $ret .= $html;
 636                 return $ret;
 637         }
 638
 639         /**
 640          * Determines if the given mime type is xml.
 641          *
 642          * @param $mimetype    string MimeType
 643          * @return Boolean
 644          */
 645         public static function isXmlMimeType( $mimetype ) {
 646                 switch ( $mimetype ) {
 647                         case 'text/xml':
 648                         case 'application/xhtml+xml':
 649                         case 'application/xml':
 650                                 return true;
 651                         default:
 652                                 return false;
 653                 }
 654         }
 655 }