title: How to use isset() in delphi
body: <p>I'm looking for the conversion from the PHP code to Delphi. Currently, i'm stuck when handling with the Isset() function in PHP code. Are there any way i can convert the below code into Delphi ?  </p>
  
  <pre><code>$collection = array(
  'doc1' =&gt;'php powerbuilder',
  'doc2' =&gt;'php visual'); 
  $dictionary = array();
  $docCount = array();    
  foreach ($collection as $docID =&gt; $doc) {
          $doc = strtolower($doc);
          $terms = explode(' ', $doc);
          $docCount[$docID] = count($terms);
          foreach ($terms as $term) {
              if (!isset($dictionary[$term])) {
                  $dictionary[$term] = array('df' =&gt; 0, 'postings' =&gt; array());
              }
  
              if (!isset($dictionary[$term]['postings'][$docID])) {
                  $dictionary[$term]['df']++;
                  $dictionary[$term]['postings'][$docID] = array('tf' =&gt; 0);
              }
              $dictionary[$term]['postings'][$docID]['tf']++;
          }
      }
  </code></pre>