title: preg_match_all explanation
body: <p>I'm guessing about the exact working of this function in PHP: <code>preg_match_all</code></p>
  
  <pre><code>$var = "Example";
  $n = preg_match_all('/[AEIOU]/i', strtoupper($var), $matches);
  
  echo "$n&lt;p&gt;"; // Output: 3
  echo $matches[0][1]; // Output: A
  </code></pre>
  
  <p>This is almost perfectly clear to me: Find all the matches of vowels in variable <code>$var</code> and put their number in <code>$n</code>, while the matches found go in the variable <code>$matches</code>. But why <code>$matches</code> is a bidimensional array if the first index must be 0? Shouldn't it be something like <code>$matches[1]</code>? (but it doesn't work)</p>
  
  <p>How can I take advantage of next indexes?</p>