title: How are \r \t and \n different from one another?
body: <p>In the code below, I don't know how these characters are different functionally from one another: \r \t \n.  Does anyone have an explanation or description for these?</p>
  
  <p>Here is some sample code:</p>
  
  <pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt;
      &lt;head&gt;
          &lt;title&gt;Sorting words in a block of text by length&lt;/title&gt;
          &lt;link rel="stylesheet" type="text/css" href="common.css" /&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;h1&gt;Sorting words in a block of text by length&lt;/h1&gt;
  
  &lt;?php
  
  $myText = &lt;&lt;&lt;END_TEXT
  But think not that this famous town has 
  only harpooneers, cannibals, and 
  bumpkins to show her visitors. Not at 
  all. Still New Bedford is a queer place. 
  Had it not been for us whalemen, that 
  tract of land would this day perhaps 
  have been in as howling condition as the 
  coast of Labrador.
  END_TEXT;
  
  echo "&lt;h2&gt;The text:&lt;/h2&gt;";
  echo "&lt;div style=\"width: 30em;\"&gt;$myText&lt;/div&gt;";
  
  $myText = preg_replace( "/[\,\.]/", "", $myText );
  $words = array_unique( preg_split( "/[ \n\r\t]+/", $myText ) );
  usort( $words, create_function( '$a, $b', 'return strlen($a) - strlen($b);
  ' ) );
  
  echo "&lt;h2&gt;The sorted words:&lt;/h2&gt;";
  echo "&lt;div style=\"width: 30em;\"&gt;";
  
  foreach ( $words as $word ) {
      echo "$word ";
  }
  echo "&lt;/div&gt;";
  
  ?&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>