title: exec and only variables should be passed by reference
body: <p>I'm using the <a href="http://faq.1and1.com/web_space__access/mysql/13.html" rel="nofollow">PHP export script from 1 and 1</a>:</p>
  
  <pre><code>&lt;?php
  //ENTER THE RELEVANT INFO BELOW
  $mysqlDatabaseName ='db123456789';
  $mysqlUserName ='dbo123456789';
  $mysqlPassword ='myPassword';
  $mysqlHostName ='db1234.perfora.net';
  $mysqlExportPath ='chooseFilenameForBackup.sql';
  
  //DONT EDIT BELOW THIS LINE
  //Export the database and output the status to the page
  $command='mysqldump --opt -h' .$mysqlHostName .' -u' .$mysqlUserName .' -p' .$mysqlPassword .' ' .$mysqlDatabaseName .' &gt; ~/' .$mysqlExportPath;
  exec($command,$output=array(),$worked);
  switch($worked){
      case 0:
          echo 'Database &lt;b&gt;' .$mysqlDatabaseName .'&lt;/b&gt; successfully exported to &lt;b&gt;~/' .$mysqlExportPath .'&lt;/b&gt;';
          break;
      case 1:
          echo 'There was a warning during the export of &lt;b&gt;' .$mysqlDatabaseName .'&lt;/b&gt; to &lt;b&gt;~/' .$mysqlExportPath .'&lt;/b&gt;';
          break;
      case 2:
          echo 'There was an error during export. Please check your values:&lt;br/&gt;&lt;br/&gt;&lt;table&gt;&lt;tr&gt;&lt;td&gt;MySQL Database Name:&lt;/td&gt;&lt;td&gt;&lt;b&gt;' .$mysqlDatabaseName .'&lt;/b&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td&gt;MySQL User Name:&lt;/td&gt;&lt;td&gt;&lt;b&gt;' .$mysqlUserName .'&lt;/b&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td&gt;MySQL Password:&lt;/td&gt;&lt;td&gt;&lt;b&gt;NOTSHOWN&lt;/b&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td&gt;MySQL Host Name:&lt;/td&gt;&lt;td&gt;&lt;b&gt;' .$mysqlHostName .'&lt;/b&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;';
          break;
  }
  ?&gt;   
  </code></pre>
  
  <p>If I'm executing it I get <code>Strict Standards: Only variables should be passed by reference in</code> and it points to this line</p>
  
  <pre><code>exec($command,$output=array(),$worked);
  </code></pre>
  
  <p>How should I adapt the script?</p>