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         public static function element( $element, $attribs = array(), $contents = '' ) {
 137                 return self::rawElement( $element, $attribs, strtr( $contents, array(
 138                         # There's no point in escaping quotes, >, etc. in the contents of
 139                         # elements.
 140                         '&' => '&amp;',
 141                         '<' => '&lt;'
 142                 ) ) );
 143         }
 144
 145         /**
 146          * Identical to rawElement(), but has no third parameter and omits the end
 147          * tag (and the self-closing '/' in XML mode for empty elements).
 148          */
 149         public static function openElement( $element, $attribs = array() ) {
 150                 global $wgHtml5, $wgWellFormedXml;
 151                 $attribs = (array)$attribs;
 152                 # This is not required in HTML5, but let's do it anyway, for
 153                 # consistency and better compression.
 154                 $element = strtolower( $element );
 155
 156                 # In text/html, initial <html> and <head> tags can be omitted under
 157                 # pretty much any sane circumstances, if they have no attributes.  See:
 158                 # <http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#optional-tags>
 159                 if ( !$wgWellFormedXml && !$attribs
 160                 && in_array( $element, array( 'html', 'head' ) ) ) {
 161                         return '';
 162                 }
 163
 164                 # Remove HTML5-only attributes if we aren't doing HTML5, and disable
 165                 # form validation regardless (see bug 23769 and the more detailed
 166                 # comment in expandAttributes())
 167                 if ( $element == 'input' ) {
 168                         # Whitelist of types that don't cause validation.  All except
 169                         # 'search' are valid in XHTML1.
 170                         $validTypes = array(
 171                                 'hidden',
 172                                 'text',
 173                                 'password',
 174                                 'checkbox',
 175                                 'radio',
 176                                 'file',
 177                                 'submit',
 178                                 'image',
 179                                 'reset',
 180                                 'button',
 181                                 'search',
 182                         );
 183                         if ( isset( $attribs['type'] )
 184                         && !in_array( $attribs['type'], $validTypes ) ) {
 185                                 unset( $attribs['type'] );
 186                         }
 187                         if ( isset( $attribs['type'] ) && $attribs['type'] == 'search'
 188                         && !$wgHtml5 ) {
 189                                 unset( $attribs['type'] );
 190                         }
 191                 }
 192                 if ( !$wgHtml5 && $element == 'textarea' && isset( $attribs['maxlength'] ) ) {
 193                         unset( $attribs['maxlength'] );
 194                 }
 195
 196                 return "<$element" . self::expandAttributes(
 197                         self::dropDefaults( $element, $attribs ) ) . '>';
 198         }
 199
 200         /**
 201          * Returns "</$element>", except if $wgWellFormedXml is off, in which case
 202          * it returns the empty string when that's guaranteed to be safe.
 203          *
 204          * @param $element string Name of the element, e.g., 'a'
 205          * @return string A closing tag, if required
 206          */
 207         public static function closeElement( $element ) {
 208                 global $wgWellFormedXml;
 209
 210                 $element = strtolower( $element );
 211
 212                 # Reference:
 213                 # http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#optional-tags
 214                 if ( !$wgWellFormedXml && in_array( $element, array(
 215                         'html',
 216                         'head',
 217                         'body',
 218                         'li',
 219                         'dt',
 220                         'dd',
 221                         'tr',
 222                         'td',
 223                         'th',
 224                 ) ) ) {
 225                         return '';
 226                 }
 227                 return "</$element>";
 228         }
 229
 230         /**
 231          * Given an element name and an associative array of element attributes,
 232          * return an array that is functionally identical to the input array, but
 233          * possibly smaller.  In particular, attributes might be stripped if they
 234          * are given their default values.
 235          *
 236          * This method is not guaranteed to remove all redundant attributes, only
 237          * some common ones and some others selected arbitrarily at random.  It
 238          * only guarantees that the output array should be functionally identical
 239          * to the input array (currently per the HTML 5 draft as of 2009-09-06).
 240          *
 241          * @param $element string Name of the element, e.g., 'a'
 242          * @param $attribs array  Associative array of attributes, e.g., array(
 243          *   'href' => 'http://www.mediawiki.org/' ).  See expandAttributes() for
 244          *   further documentation.
 245          * @return array An array of attributes functionally identical to $attribs
 246          */
 247         private static function dropDefaults( $element, $attribs ) {
 248                 # Don't bother doing anything if we aren't outputting HTML5; it's too
 249                 # much of a pain to maintain two sets of defaults.
 250                 global $wgHtml5;
 251                 if ( !$wgHtml5 ) {
 252                         return $attribs;
 253                 }
 254
 255                 static $attribDefaults = array(
 256                         'area' => array( 'shape' => 'rect' ),
 257                         'button' => array(
 258                                 'formaction' => 'GET',
 259                                 'formenctype' => 'application/x-www-form-urlencoded',
 260                                 'type' => 'submit',
 261                         ),
 262                         'canvas' => array(
 263                                 'height' => '150',
 264                                 'width' => '300',
 265                         ),
 266                         'command' => array( 'type' => 'command' ),
 267                         'form' => array(
 268                                 'action' => 'GET',
 269                                 'autocomplete' => 'on',
 270                                 'enctype' => 'application/x-www-form-urlencoded',
 271                         ),
 272                         'input' => array(
 273                                 'formaction' => 'GET',
 274                                 'type' => 'text',
 275                                 'value' => '',
 276                         ),
 277                         'keygen' => array( 'keytype' => 'rsa' ),
 278                         'link' => array( 'media' => 'all' ),
 279                         'menu' => array( 'type' => 'list' ),
 280                         # Note: the use of text/javascript here instead of other JavaScript
 281                         # MIME types follows the HTML5 spec.
 282                         'script' => array( 'type' => 'text/javascript' ),
 283                         'style' => array(
 284                                 'media' => 'all',
 285                                 'type' => 'text/css',
 286                         ),
 287                         'textarea' => array( 'wrap' => 'soft' ),
 288                 );
 289
 290                 $element = strtolower( $element );
 291
 292                 foreach ( $attribs as $attrib => $value ) {
 293                         $lcattrib = strtolower( $attrib );
 294                         $value = strval( $value );
 295
 296                         # Simple checks using $attribDefaults
 297                         if ( isset( $attribDefaults[$element][$lcattrib] ) &&
 298                         $attribDefaults[$element][$lcattrib] == $value ) {
 299                                 unset( $attribs[$attrib] );
 300                         }
 301
 302                         if ( $lcattrib == 'class' && $value == '' ) {
 303                                 unset( $attribs[$attrib] );
 304                         }
 305                 }
 306
 307                 # More subtle checks
 308                 if ( $element === 'link' && isset( $attribs['type'] )
 309                 && strval( $attribs['type'] ) == 'text/css' ) {
 310                         unset( $attribs['type'] );
 311                 }
 312                 if ( $element === 'select' && isset( $attribs['size'] ) ) {
 313                         if ( in_array( 'multiple', $attribs )
 314                                 || ( isset( $attribs['multiple'] ) && $attribs['multiple'] !== false )
 315                         ) {
 316                                 # A multi-select
 317                                 if ( strval( $attribs['size'] ) == '4' ) {
 318                                         unset( $attribs['size'] );
 319                                 }
 320                         } else {
 321                                 # Single select
 322                                 if ( strval( $attribs['size'] ) == '1' ) {
 323                                         unset( $attribs['size'] );
 324                                 }
 325                         }
 326                 }
 327
 328                 return $attribs;
 329         }
 330
 331         /**
 332          * Given an associative array of element attributes, generate a string
 333          * to stick after the element name in HTML output.  Like array( 'href' =>
 334          * 'http://www.mediawiki.org/' ) becomes something like
 335          * ' href="http://www.mediawiki.org"'.  Again, this is like
 336          * Xml::expandAttributes(), but it implements some HTML-specific logic.
 337          * For instance, it will omit quotation marks if $wgWellFormedXml is false,
 338          * and will treat boolean attributes specially.
 339          *
 340          * @param $attribs array Associative array of attributes, e.g., array(
 341          *   'href' => 'http://www.mediawiki.org/' ).  Values will be HTML-escaped.
 342          *   A value of false means to omit the attribute.  For boolean attributes,
 343          *   you can omit the key, e.g., array( 'checked' ) instead of
 344          *   array( 'checked' => 'checked' ) or such.
 345          * @return string HTML fragment that goes between element name and '>'
 346          *   (starting with a space if at least one attribute is output)
 347          */
 348         public static function expandAttributes( $attribs ) {
 349                 global $wgHtml5, $wgWellFormedXml;
 350
 351                 $ret = '';
 352                 $attribs = (array)$attribs;
 353                 foreach ( $attribs as $key => $value ) {
 354                         if ( $value === false ) {
 355                                 continue;
 356                         }
 357
 358                         # For boolean attributes, support array( 'foo' ) instead of
 359                         # requiring array( 'foo' => 'meaningless' ).
 360                         if ( is_int( $key )
 361                         && in_array( strtolower( $value ), self::$boolAttribs ) ) {
 362                                 $key = $value;
 363                         }
 364
 365                         # Not technically required in HTML5, but required in XHTML 1.0,
 366                         # and we'd like consistency and better compression anyway.
 367                         $key = strtolower( $key );
 368
 369                         # Bug 23769: Blacklist all form validation attributes for now.  Current
 370                         # (June 2010) WebKit has no UI, so the form just refuses to submit
 371                         # without telling the user why, which is much worse than failing
 372                         # server-side validation.  Opera is the only other implementation at
 373                         # this time, and has ugly UI, so just kill the feature entirely until
 374                         # we have at least one good implementation.
 375                         if ( in_array( $key, array( 'max', 'min', 'pattern', 'required', 'step' ) ) ) {
 376                                 continue;
 377                         }
 378
 379                         # Here we're blacklisting some HTML5-only attributes...
 380                         if ( !$wgHtml5 && in_array( $key, array(
 381                                         'autocomplete',
 382                                         'autofocus',
 383                                         'max',
 384                                         'min',
 385                                         'multiple',
 386                                         'pattern',
 387                                         'placeholder',
 388                                         'required',
 389                                         'step',
 390                                         'spellcheck',
 391                         ) ) ) {
 392                                 continue;
 393                         }
 394
 395                         # See the "Attributes" section in the HTML syntax part of HTML5,
 396                         # 9.1.2.3 as of 2009-08-10.  Most attributes can have quotation
 397                         # marks omitted, but not all.  (Although a literal " is not
 398                         # permitted, we don't check for that, since it will be escaped
 399                         # anyway.)
 400                         #
 401                         # See also research done on further characters that need to be
 402                         # escaped: http://code.google.com/p/html5lib/issues/detail?id=93
 403                         $badChars = "\\x00- '=<>`/\x{00a0}\x{1680}\x{180e}\x{180F}\x{2000}\x{2001}"
 404                                 . "\x{2002}\x{2003}\x{2004}\x{2005}\x{2006}\x{2007}\x{2008}\x{2009}"
 405                                 . "\x{200A}\x{2028}\x{2029}\x{202F}\x{205F}\x{3000}";
 406                         if ( $wgWellFormedXml || $value === ''
 407                         || preg_match( "![$badChars]!u", $value ) ) {
 408                                 $quote = '"';
 409                         } else {
 410                                 $quote = '';
 411                         }
 412
 413                         if ( in_array( $key, self::$boolAttribs ) ) {
 414                                 # In XHTML 1.0 Transitional, the value needs to be equal to the
 415                                 # key.  In HTML5, we can leave the value empty instead.  If we
 416                                 # don't need well-formed XML, we can omit the = entirely.
 417                                 if ( !$wgWellFormedXml ) {
 418                                         $ret .= " $key";
 419                                 } elseif ( $wgHtml5 ) {
 420                                         $ret .= " $key=\"\"";
 421                                 } else {
 422                                         $ret .= " $key=\"$key\"";
 423                                 }
 424                         } else {
 425                                 # Apparently we need to entity-encode \n, \r, \t, although the
 426                                 # spec doesn't mention that.  Since we're doing strtr() anyway,
 427                                 # and we don't need <> escaped here, we may as well not call
 428                                 # htmlspecialchars().  FIXME: verify that we actually need to
 429                                 # escape \n\r\t here, and explain why, exactly.
 430                                 #
 431                                 # We could call Sanitizer::encodeAttribute() for this, but we
 432                                 # don't because we're stubborn and like our marginal savings on
 433                                 # byte size from not having to encode unnecessary quotes.
 434                                 $map = array(
 435                                         '&' => '&amp;',
 436                                         '"' => '&quot;',
 437                                         "\n" => '&#10;',
 438                                         "\r" => '&#13;',
 439                                         "\t" => '&#9;'
 440                                 );
 441                                 if ( $wgWellFormedXml ) {
 442                                         # This is allowed per spec: <http://www.w3.org/TR/xml/#NT-AttValue>
 443                                         # But reportedly it breaks some XML tools?  FIXME: is this
 444                                         # really true?
 445                                         $map['<'] = '&lt;';
 446                                 }
 447                                 $ret .= " $key=$quote" . strtr( $value, $map ) . $quote;
 448                         }
 449                 }
 450                 return $ret;
 451         }
 452
 453         /**
 454          * Output a <script> tag with the given contents.  TODO: do some useful
 455          * escaping as well, like if $contents contains literal '</script>' or (for
 456          * XML) literal "]]>".
 457          *
 458          * @param $contents string JavaScript
 459          * @return string Raw HTML
 460          */
 461         public static function inlineScript( $contents ) {
 462                 global $wgHtml5, $wgJsMimeType, $wgWellFormedXml;
 463
 464                 $attrs = array();
 465                 if ( !$wgHtml5 ) {
 466                         $attrs['type'] = $wgJsMimeType;
 467                 }
 468                 if ( $wgWellFormedXml && preg_match( '/[<&]/', $contents ) ) {
 469                         $contents = "/*<![CDATA[*/$contents/*]]>*/";
 470                 }
 471                 return self::rawElement( 'script', $attrs, $contents );
 472         }
 473
 474         /**
 475          * Output a <script> tag linking to the given URL, e.g.,
 476          * <script src=foo.js></script>.
 477          *
 478          * @param $url string
 479          * @return string Raw HTML
 480          */
 481         public static function linkedScript( $url ) {
 482                 global $wgHtml5, $wgJsMimeType;
 483
 484                 $attrs = array( 'src' => $url );
 485                 if ( !$wgHtml5 ) {
 486                         $attrs['type'] = $wgJsMimeType;
 487                 }
 488                 return self::element( 'script', $attrs );
 489         }
 490
 491         /**
 492          * Output a <style> tag with the given contents for the given media type
 493          * (if any).  TODO: do some useful escaping as well, like if $contents
 494          * contains literal '</style>' (admittedly unlikely).
 495          *
 496          * @param $contents string CSS
 497          * @param $media mixed A media type string, like 'screen'
 498          * @return string Raw HTML
 499          */
 500         public static function inlineStyle( $contents, $media = 'all' ) {
 501                 global $wgWellFormedXml;
 502
 503                 if ( $wgWellFormedXml && preg_match( '/[<&]/', $contents ) ) {
 504                         $contents = "/*<![CDATA[*/$contents/*]]>*/";
 505                 }
 506                 return self::rawElement( 'style', array(
 507                         'type' => 'text/css',
 508                         'media' => $media,
 509                 ), $contents );
 510         }
 511
 512         /**
 513          * Output a <link rel=stylesheet> linking to the given URL for the given
 514          * media type (if any).
 515          *
 516          * @param $url string
 517          * @param $media mixed A media type string, like 'screen'
 518          * @return string Raw HTML
 519          */
 520         public static function linkedStyle( $url, $media = 'all' ) {
 521                 return self::element( 'link', array(
 522                         'rel' => 'stylesheet',
 523                         'href' => $url,
 524                         'type' => 'text/css',
 525                         'media' => $media,
 526                 ) );
 527         }
 528
 529         /**
 530          * Convenience function to produce an <input> element.  This supports the
 531          * new HTML5 input types and attributes, and will silently strip them if
 532          * $wgHtml5 is false.
 533          *
 534          * @param $name    string name attribute
 535          * @param $value   mixed  value attribute
 536          * @param $type    string type attribute
 537          * @param $attribs array  Associative array of miscellaneous extra
 538          *   attributes, passed to Html::element()
 539          * @return string Raw HTML
 540          */
 541         public static function input( $name, $value = '', $type = 'text', $attribs = array() ) {
 542                 $attribs['type'] = $type;
 543                 $attribs['value'] = $value;
 544                 $attribs['name'] = $name;
 545
 546                 return self::element( 'input', $attribs );
 547         }
 548
 549         /**
 550          * Convenience function to produce an input element with type=hidden
 551          *
 552          * @param $name    string name attribute
 553          * @param $value   string value attribute
 554          * @param $attribs array  Associative array of miscellaneous extra
 555          *   attributes, passed to Html::element()
 556          * @return string Raw HTML
 557          */
 558         public static function hidden( $name, $value, $attribs = array() ) {
 559                 return self::input( $name, $value, 'hidden', $attribs );
 560         }
 561
 562         /**
 563          * Convenience function to produce an <input> element.  This supports leaving
 564          * out the cols= and rows= which Xml requires and are required by HTML4/XHTML
 565          * but not required by HTML5 and will silently set cols="" and rows="" if
 566          * $wgHtml5 is false and cols and rows are omitted (HTML4 validates present
 567          * but empty cols="" and rows="" as valid).
 568          *
 569          * @param $name    string name attribute
 570          * @param $value   string value attribute
 571          * @param $attribs array  Associative array of miscellaneous extra
 572          *   attributes, passed to Html::element()
 573          * @return string Raw HTML
 574          */
 575         public static function textarea( $name, $value = '', $attribs = array() ) {
 576                 global $wgHtml5;
 577                 $attribs['name'] = $name;
 578                 if ( !$wgHtml5 ) {
 579                         if ( !isset( $attribs['cols'] ) ) {
 580                                 $attribs['cols'] = "";
 581                         }
 582                         if ( !isset( $attribs['rows'] ) ) {
 583                                 $attribs['rows'] = "";
 584                         }
 585                 }
 586                 return self::element( 'textarea', $attribs, $value );
 587         }
 588
 589         /**
 590          * Constructs the opening html-tag with necessary doctypes depending on
 591          * global variables.
 592          *
 593          * @param $attribs array  Associative array of miscellaneous extra
 594          *   attributes, passed to Html::element() of html tag.
 595          * @return string  Raw HTML
 596          */
 597         public static function htmlHeader( $attribs = array() ) {
 598                 $ret = '';
 599
 600                 global $wgMimeType, $wgOutputEncoding;
 601                 if ( self::isXmlMimeType( $wgMimeType ) ) {
 602                         $ret .= "<?xml version=\"1.0\" encoding=\"$wgOutputEncoding\" ?" . ">\n";
 603                 }
 604
 605                 global $wgHtml5, $wgHtml5Version, $wgDocType, $wgDTD;
 606                 global $wgXhtmlNamespaces, $wgXhtmlDefaultNamespace;
 607                 if ( $wgHtml5 ) {
 608                         $ret .= "<!DOCTYPE html>\n";
 609                         if ( $wgHtml5Version ) {
 610                                 $attribs['version'] = $wgHtml5Version;
 611                         }
 612                 } else {
 613                         $ret .= "<!DOCTYPE html PUBLIC \"$wgDocType\" \"$wgDTD\">\n";
 614                         $attribs['xmlns'] = $wgXhtmlDefaultNamespace;
 615                         foreach ( $wgXhtmlNamespaces as $tag => $ns ) {
 616                                 $attribs["xmlns:$tag"] = $ns;
 617                         }
 618                 }
 619                 $html = Html::openElement( 'html', $attribs );
 620                 if ( $html ) {
 621                         $html .= "\n";
 622                 }
 623                 $ret .= $html;
 624                 return $ret;
 625         }
 626
 627         /**
 628          * Determines if the given mime type is xml.
 629          *
 630          * @param $mimetype    string MimeType
 631          * @return Boolean
 632          */
 633         public static function isXmlMimeType( $mimetype ) {
 634                 switch ( $mimetype ) {
 635                         case 'text/xml':
 636                         case 'application/xhtml+xml':
 637                         case 'application/xml':
 638                                 return true;
 639                         default:
 640                                 return false;
 641                 }
 642         }
 643 }