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  22  <p>
  23  <h1>MagpieRSS Recipes:  Cooking with Corbies</h1>
  24  
  25  <div align="center"><h3><em>"Four and twenty blackbirds baked in a
  26  pie."</em></h3></div>
  27  </p>
  28  <p>
  29  <ol>
  30  <li><a href="#limit">Limit the Number of Headlines(aka Items) Returned</a></li>
  31  <li><a href="#error_message">Display a Custom Error Message if Something Goes
  32  Wrong</a></li>
  33  <li><a href="#write_rss">Generate a New RSS Feed</a></li>
  34  <li><a href="#by_date">Display Headlines More Recent then X Date</a></li>
  35  <li><a href="#from_file">Parse a Local File Containing RSS</a></li>
  36  
  37  </ol>
  38  </p>
  39  
  40  <a name="limit"></a><h2>1. Limit the Number of Headlines(aka Items) Returned.</h2>
  41  
  42  <h3>Problem:</h3>
  43  
  44  You want to display the 10 (or 3 or whatever) most recent headlines, but the RSS feed
  45  contains 15.
  46  
  47  <h3>Solution:</h3>
  48  
  49  <pre>
  50  $num_items = 10;
  51  $rss = fetch_rss($url);
  52  
  53  $items = array_slice($rss->items, 0, $num_items);
  54  
  55  foreach ( $items as $item ) {
  56  </pre>
  57  <h3>Discussion:</h3>
  58  
  59  Rather then trying to limit the number of items Magpie parses, a much simpler,
  60  and more flexible approach is to take a "slice" of the array of items.  And
  61  array_slice() is smart enough to do the right thing if the feed has less items
  62  then $num_items.
  63  
  64  <h3>See:</h3> <a href="http://www.php.net/array_slice">http://www.php.net/array_slice</a>
  65  </p>
  66  
  67  <a name="error_message"></a><h2>2. Display a Custom Error Message if Something Goes Wrong</h2>
  68  
  69  <h3>Problem:</h3>
  70  
  71  You don't want Magpie's error messages showing up if something goes wrong.
  72  
  73  <h3>Solution:</h3>
  74  <pre>
  75  # Magpie throws USER_WARNINGS only
  76  # so you can cloak these, by only showing ERRORs
  77  error_reporting(E_ERROR);
  78  
  79  # check the return value of fetch_rss()
  80  
  81  $rss = fetch_rss($url);
  82  
  83  if ( $rss ) {
  84  ...display rss feed...
  85  }
  86  else {
  87     echo "An error occured!  " .
  88          "Consider donating more $$$ for restoration of services." .
  89          "&lt;br&gt;Error Message: " . magpie_error();
  90  }
  91  </pre>
  92  <h3>Discussion:</h3>
  93  
  94  MagpieRSS triggers a warning in a number of circumstances.  The 2 most common
  95  circumstances are:  if the specified RSS file isn't properly formed (usually
  96  because it includes illegal HTML), or if Magpie can't download the remote RSS
  97  file, and there is no cached version.  
  98  
  99  If you don't want your users to see these warnings change your error_reporting
 100  settings to only display ERRORs.<br />
 101  Another option is to turn off display_error,
 102  so that WARNINGs, and NOTICEs still go to the error_log but not to the webpages.
 103  
 104  You can do this with:
 105  
 106  <pre>
 107  # you can also do this in your php.ini file
 108  ini_set('display_errors', 0);
 109  </pre>
 110  
 111  <h3>See:</h3>
 112  <a
 113  href="http://www.php.net/error_reporting">http://www.php.net/error_reporting</a>,<br
 114  />
 115  <a href="http://www.php.net/ini_set">http://www.php.net/ini_set</a>, <br />
 116  <a
 117  href="http://www.php.net/manual/en/ref.errorfunc.php">http://www.php.net/manual/en/ref.errorfunc.php</a><br
 118  />
 119  
 120  <a name="write_rss"></a><h2>3. Generate a New RSS Feed</h2>
 121  
 122  <h3>Problem:</h3>
 123  
 124  Create an RSS feed for other people to use.
 125  
 126  <h3>Solution:</h3>
 127  
 128  Use Useful Inc's <a href="http://usefulinc.com/rss/rsswriter/">RSSWriter</a>.
 129  
 130  <h3>Discussion:</h3>
 131  
 132  An example of turning a Magpie parsed RSS object back into an RSS file is
 133  forthcoming.  In the meantime RSSWriter is well documented.
 134  
 135  <a name="by_date"></a><h2>4. Display Headlines More Recent then X Date</h2>
 136  
 137  <h3>Problem:</h3>
 138  
 139  You only want to display headlines that were published on, or after a certain
 140  date.
 141  
 142  
 143  <h3>Solution:</h3>
 144  <pre>
 145  require_once ('rss_utils.inc');
 146  
 147  # get all headlines published today
 148  $today = getdate();
 149  
 150  # today, 12AM
 151  $date = mktime(0,0,0,$today['mon'], $today['mday'], $today['year']);
 152  
 153  $rss = fetch_rss($url);
 154  
 155  foreach ( $rss->items as $item ) {
 156     $published = parse_w3cdtf($item['dc']['date']);
 157     if ( $published &gt;= $date ) {
 158          echo "Title: " . $item['title'];
 159          echo "Published: " . date("h:i:s A", $published);
 160          echo "&lt;p&gt;";
 161      }
 162  }
 163  </pre>
 164  <h3>Discussion:</h3>
 165  
 166  This recipe only works for RSS 1.0 feeds that include the <dc:date> field.
 167  (which is very good RSS style) <br /> 
 168  <code>parse_w3cdtf()</code> is defined in
 169  <code>rss_utils.inc</code>, and parses RSS style dates into Unix epoch
 170  seconds.  
 171  
 172  <h3>See: </h3>
 173  <a
 174  href="http://www.php.net/manual/en/ref.datetime.php">http://www.php.net/manual/en/ref.datetime.php</a>
 175  
 176  <a name="from_file"></a>
 177  <h2>5. Parse a Local File Containing RSS</h2>
 178  <h3>Problem:</h3>
 179  MagpieRSS provides <code>fetch_rss()</code> which takes a URL and returns a
 180  parsed RSS object, but what if you want to parse a file stored locally that
 181  doesn't have a URL?
 182  
 183  <h3>Solution</h3>
 184  <pre>
 185  require_once ('rss_parse.inc');
 186  
 187  $rss_file = 'some_rss_file.rdf';
 188  $rss_string = read_file($rss_file);
 189  $rss = new MagpieRSS( $rss_string );
 190  
 191  if ( $rss and !$rss->ERROR) {
 192  ...display rss...
 193  }
 194  else {
 195      echo "Error: " . $rss->ERROR;
 196  }
 197  
 198  # efficiently read a file into a string
 199  # in php >= 4.3.0 you can simply use file_get_contents()
 200  #
 201  function read_file($filename) {
 202      $fh = fopen($filename, 'r') or die($php_errormsg);
 203      $rss_string = fread($fh, filesize($filename) );
 204      fclose($fh);
 205      return $rss_string;
 206  }
 207  </pre>
 208  
 209  <h3>Discussion</h3>
 210  Here we are using MagpieRSS's RSS parser directly without the convience wrapper
 211  of <code>fetch_rss()</code>.  We read the contents of the RSS file into a
 212  string, and pass it to the parser constructor.  Notice also that error handling
 213  is subtly different.
 214  
 215  <h3>See: </h3>
 216  <a
 217  href="http://www.php.net/manual/en/ref.filesystem.php">http://www.php.net/manual/en/ref.filesystem.php</a>,<br
 218  />
 219  <a
 220  href="http://www.php.net/manual/en/language.oop.php">http://www.php.net/manual/en/language.oop.php</a>
 221  
 222  <!-- 
 223  <a name="link"></a><h2>#. Recipe</h2>
 224  <h3>Problem:</h3>
 225  Problem description
 226  <h3>Solution</h3>
 227  <pre>
 228  code
 229  </pre>
 230  <h3>Discussion/h3>
 231  Discuss code
 232  <h3>See: </h3>
 233  Documentation links:
 234  -->
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