How to fix the invisible space problem in PHP?
<p>As a result,functions like <code>session_start</code> and <code>setcookie</code> can't run successfully,reporting:</p>

<blockquote>
  <p>Cannot modify header information -
  headers already sent by</p>
</blockquote>

<p>But the target file is like this:</p>

<pre><code>1 &lt;?php
2 session_start();
</code></pre>

<p>How to fix it?</p>

<p><strong>FOUNDINGS</strong></p>

<p>I've found the problem,the utf-8 formated files become utf-8+BOM after uploading to the server,so I've temporarily solved the problem by saving it as utf-8 again.</p>

<p><strong>BUT</strong>,there are lots of other files with the same problem,how can I batch solve the issue?</p>
