title: Can PHP's echo/print_r functions somehow print words like NULL and false?
body: <p>Unlike <code>var_dump</code> or <code>var_export</code> the functions <code>echo</code> and <code>print_r</code> seem to display blanks instead of words like NULL and false.</p>
  <p>For example, with <code>print_r</code>:</p>
  <pre><code>&lt;?php
  $arr = array('one' =&gt; true, 'zero' =&gt; false, 'null' =&gt; null, 'recursive' =&gt; array(1=&gt;array(2=&gt;3)));
  echo '&lt;pre&gt;' . print_r($arr, true) . '&lt;/pre&gt;'; // Array
  echo '&lt;pre&gt;' . var_export($arr, true) . '&lt;/pre&gt;'; // String =&gt; gettype(var_export($arr)); returns string
  ?&gt;
  
  Array
  (
      [one] =&gt; 1
      [zero] =&gt; 
      [null] =&gt; 
      [recursive] =&gt; Array
          (
              [1] =&gt; Array
                  (
                      [2] =&gt; 3
                  )
          )
  )
  
  array (
    'one' =&gt; true,
    'zero' =&gt; false,
    'null' =&gt; NULL,
    'recursive' =&gt; 
    array (
      1 =&gt; 
      array (
        2 =&gt; 3,
      ),
    ),
  )
  </code></pre>
  <p><code>var_dump/export</code> aren't nearly as nicely readable as <code>echo</code> and even more so <code>print_r</code>, so can anything be done to show such words in <code>print_r</code> and <code>echo</code>?</p>