title: preg_match for multiple words
body: <p>I want to test a string to see it contains certain words.</p>
  <p>i.e:</p>
  <pre><code>$string = &quot;The rain in spain is certain as the dry on the plain is over and it is not clear&quot;;
  preg_match('`\brain\b`',$string);
  </code></pre>
  <p>But that method only matches one word. How do I check for multiple words?</p>