title: PHP preg_replace number of digits
body: <p>i have this:</p>
  
  <pre><code>preg_replace('/(\d{1}|\d{2})/gi', '$1', 'some number');
  </code></pre>
  
  <p>If text is one digit number $1 returns one digit number, if it is 2 digit it return 2 digit number...., but I need to returned number was always been 2 digit:</p>
  
  <pre><code>1 =&gt; 01 
  2 =&gt; 02
  ...
  10 =&gt; 10
  ...
  99 =&gt; 99
  </code></pre>
  
  <p>How can I do that?</p>