Detailed explanation of the steps to obtain file mime types in PHP

<?php
/*
 * Copyright 2010-2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 * http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */
/*%******************************************************************************************%*/
// CLASS
/**
 * Simplifies the process of looking up the content-types for a variety of file extensions.
 *
 * @version 2010.07.20
 * @license See the included NOTICE.md file for more information.
 * @copyright See the included NOTICE.md file for more information.
 * @link http://aws.amazon.com/php/ PHP Developer Center
 */
class CFMimeTypes
{
  /**
   * Map of the extension-to-mime-types that we support.
   */
  public static $mime_types = array(
    &#39;3gp&#39; => 'video/3gpp',
    'ai' => 'application/postscript',
    'aif' => 'audio/x-aiff',
    'aifc' => 'audio/x-aiff',
    'aiff' => 'audio/x-aiff',
    'asc' => 'text/plain',
    'atom' => 'application/atom+xml',
    'au' => 'audio/basic',
    'avi' => 'video/x-msvideo',
    'bcpio' => 'application/x-bcpio',
    'bin' => 'application/octet-stream',
    'bmp' => 'image/bmp',
    'cdf' => 'application/x-netcdf',
    'cgm' => 'image/cgm',
    'class' => 'application/octet-stream',
    'cpio' => 'application/x-cpio',
    'cpt' => 'application/mac-compactpro',
    'csh' => 'application/x-csh',
    'css' => 'text/css',
    'dcr' => 'application/x-director',
    'dif' => 'video/x-dv',
    'dir' => 'application/x-director',
    'djv' => 'image/vnd.djvu',
    'djvu' => 'image/vnd.djvu',
    'dll' => 'application/octet-stream',
    'dmg' => 'application/octet-stream',
    'dms' => 'application/octet-stream',
    'doc' => 'application/msword',
    'dtd' => 'application/xml-dtd',
    'dv' => 'video/x-dv',
    'dvi' => 'application/x-dvi',
    'dxr' => 'application/x-director',
    'eps' => 'application/postscript',
    'etx' => 'text/x-setext',
    'exe' => 'application/octet-stream',
    'ez' => 'application/andrew-inset',
    'flv' => 'video/x-flv',
    'gif' => 'image/gif',
    'gram' => 'application/srgs',
    'grxml' => 'application/srgs+xml',
    'gtar' => 'application/x-gtar',
    'gz' => 'application/x-gzip',
    'hdf' => 'application/x-hdf',
    'hqx' => 'application/mac-binhex40',
    'htm' => 'text/html',
    'html' => 'text/html',
    'ice' => 'x-conference/x-cooltalk',
    'ico' => 'image/x-icon',
    'ics' => 'text/calendar',
    'ief' => 'image/ief',
    'ifb' => 'text/calendar',
    'iges' => 'model/iges',
    'igs' => 'model/iges',
    'jnlp' => 'application/x-java-jnlp-file',
    'jp2' => 'image/jp2',
    'jpe' => 'image/jpeg',
    'jpeg' => 'image/jpeg',
    'jpg' => 'image/jpeg',
    'js' => 'application/x-javascript',
    'kar' => 'audio/midi',
    'latex' => 'application/x-latex',
    'lha' => 'application/octet-stream',
    'lzh' => 'application/octet-stream',
    'm3u' => 'audio/x-mpegurl',
    'm4a' => 'audio/mp4a-latm',
    'm4p' => 'audio/mp4a-latm',
    'm4u' => 'video/vnd.mpegurl',
    'm4v' => 'video/x-m4v',
    'mac' => 'image/x-macpaint',
    'man' => 'application/x-troff-man',
    'mathml' => 'application/mathml+xml',
    'me' => 'application/x-troff-me',
    'mesh' => 'model/mesh',
    'mid' => 'audio/midi',
    'midi' => 'audio/midi',
    'mif' => 'application/vnd.mif',
    'mov' => 'video/quicktime',
    'movie' => 'video/x-sgi-movie',
    'mp2' => 'audio/mpeg',
    'mp3' => 'audio/mpeg',
    'mp4' => 'video/mp4',
    'mpe' => 'video/mpeg',
    'mpeg' => 'video/mpeg',
    'mpg' => 'video/mpeg',
    'mpga' => 'audio/mpeg',
    'ms' => 'application/x-troff-ms',
    'msh' => 'model/mesh',
    'mxu' => 'video/vnd.mpegurl',
    'nc' => 'application/x-netcdf',
    'oda' => 'application/oda',
    'ogg' => 'application/ogg',
    'ogv' => 'video/ogv',
    'pbm' => 'image/x-portable-bitmap',
    'pct' => 'image/pict',
    'pdb' => 'chemical/x-pdb',
    'pdf' => 'application/pdf',
    'pgm' => 'image/x-portable-graymap',
    'pgn' => 'application/x-chess-pgn',
    'pic' => 'image/pict',
    'pict' => 'image/pict',
    'png' => 'image/png',
    'pnm' => 'image/x-portable-anymap',
    'pnt' => 'image/x-macpaint',
    'pntg' => 'image/x-macpaint',
    'ppm' => 'image/x-portable-pixmap',
    'ppt' => 'application/vnd.ms-powerpoint',
    'ps' => 'application/postscript',
    'qt' => 'video/quicktime',
    'qti' => 'image/x-quicktime',
    'qtif' => 'image/x-quicktime',
    'ra' => 'audio/x-pn-realaudio',
    'ram' => 'audio/x-pn-realaudio',
    'ras' => 'image/x-cmu-raster',
    'rdf' => 'application/rdf+xml',
    'rgb' => 'image/x-rgb',
    'rm' => 'application/vnd.rn-realmedia',
    'roff' => 'application/x-troff',
    'rtf' => 'text/rtf',
    'rtx' => 'text/richtext',
    'sgm' => 'text/sgml',
    'sgml' => 'text/sgml',
    'sh' => 'application/x-sh',
    'shar' => 'application/x-shar',
    'silo' => 'model/mesh',
    'sit' => 'application/x-stuffit',
    'skd' => 'application/x-koan',
    'skm' => 'application/x-koan',
    'skp' => 'application/x-koan',
    'skt' => 'application/x-koan',
    'smi' => 'application/smil',
    'smil' => 'application/smil',
    'snd' => 'audio/basic',
    'so' => 'application/octet-stream',
    'spl' => 'application/x-futuresplash',
    'src' => 'application/x-wais-source',
    'sv4cpio' => 'application/x-sv4cpio',
    'sv4crc' => 'application/x-sv4crc',
    'svg' => 'image/svg+xml',
    'swf' => 'application/x-shockwave-flash',
    't' => 'application/x-troff',
    'tar' => 'application/x-tar',
    'tcl' => 'application/x-tcl',
    'tex' => 'application/x-tex',
    'texi' => 'application/x-texinfo',
    'texinfo' => 'application/x-texinfo',
    'tif' => 'image/tiff',
    'tiff' => 'image/tiff',
    'tr' => 'application/x-troff',
    'tsv' => 'text/tab-separated-values',
    'txt' => 'text/plain',
    'ustar' => 'application/x-ustar',
    'vcd' => 'application/x-cdlink',
    'vrml' => 'model/vrml',
    'vxml' => 'application/voicexml+xml',
    'wav' => 'audio/x-wav',
    'wbmp' => 'image/vnd.wap.wbmp',
    'wbxml' => 'application/vnd.wap.wbxml',
    'webm' => 'video/webm',
    'wml' => 'text/vnd.wap.wml',
    'wmlc' => 'application/vnd.wap.wmlc',
    'wmls' => 'text/vnd.wap.wmlscript',
    'wmlsc' => 'application/vnd.wap.wmlscriptc',
    'wmv' => 'video/x-ms-wmv',
    'wrl' => 'model/vrml',
    'xbm' => 'image/x-xbitmap',
    'xht' => 'application/xhtml+xml',
    'xhtml' => 'application/xhtml+xml',
    'xls' => 'application/vnd.ms-excel',
    'xml' => 'application/xml',
    'xpm' => 'image/x-xpixmap',
    'xsl' => 'application/xml',
    'xslt' => 'application/xslt+xml',
    'xul' => 'application/vnd.mozilla.xul+xml',
    'xwd' => 'image/x-xwindowdump',
    'xyz' => 'chemical/x-xyz',
    'zip' => 'application/zip',
  );
  /**
   * Attempt to match the file extension to a known mime-type.
   *
   * @param string $ext (Required) The file extension to attempt to map.
   * @return string The mime-type to use for the file extension.
   */
  public static function get_mimetype($ext)
  {
    $ext = strtolower($ext); // Make sure the passed in extension is lowercase
    return isset(self::$mime_types[$ext]) ? self::$mime_types[$ext] : 'application/octet-stream';
  }
}