title: How to replace <span style="font-weight: bold;">foo</span> by <strong>foo</strong> using PHP and regex?
body: <p>I have a string like this:</p>
  
  <pre><code>&lt;span style="font-weight: bold;"&gt;Foo&lt;/span&gt;
  </code></pre>
  
  <p>I want to use PHP to make it</p>
  
  <pre><code>&lt;strong&gt;Foo&lt;/strong&gt;
  </code></pre>
  
  <p>…without affecting other <code>span</code>s.</p>
  
  <p>How can I do this?</p>