title: how to define regex (preg_replace) to removes space between number character
body: <p>I have string like this:</p>
  
  <pre><code>$str = "old iccid : 809831 3245 345 new iccid : 999000 112221"
  </code></pre>
  
  <p>How to define regex in order to remove the space character between number character in PHP, to become this output?</p>
  
  <pre><code>$output = "old iccid : 8098313245345 new iccid : 999000112221";
  </code></pre>
  
  <p>i've tried to use this syntax:</p>
  
  <pre><code>$output = preg_replace( '/\d[ *]\d/', '', $str);
  </code></pre>
  
  <p>but didn't work well.</p>