title: preg_replace reverse/mutual replacing on synonyms words
body: <p>I want to mutual or reverse replace on synonyms words. I have to give an example to tell you:</p>
  
  <pre><code>$string = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit';
  $find = array('/ipsum/', '/amet/');
  $replace = array('amet', 'ipsum');
  $output = preg_replace($find, $replace, $string);
  </code></pre>
  
  <h3>Output is:</h3>
  
  <blockquote>
    <p>Lorem ipsum dolor sit ipsum, consectetur adipiscing elit</p>
  </blockquote>
  
  <h3>Expected output is should be like that:</h3>
  
  <blockquote>
    <p>Lorem amet dolor sit ipsum, consectetur adipiscing elit</p>
  </blockquote>
  
  <p>So i want to change all <code>ipsum</code> to <code>amet</code> and <code>amet</code> to <code>lorem</code>. These two words that "ipsum" and "amet" just samples. I have thousands synonyms words.</p>
  
  <p>Like you see, i tried <code>preg_replace</code> function but doest work.</p>