title: Syntax in function's parameters in documentation
body: <p>Can you please explain documentation syntax in functions. For example php function</p>
  
  <pre><code>int preg_match ( string $pattern , string $subject [, array &amp;$matches [, int $flags = 0 [, int $offset = 0 ]]] )
  </code></pre>
  
  <p>So far i understand that in in round brackets goes function's parameters,also that square bracket means for array. But what does that mean    <code>[,</code>
  and why there are no comma after $subject?</p>