Cannot modify header information - PHP
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/1793482/php-error-cannot-modify-header-information-headers-already-sent">PHP error: Cannot modify header information – headers already sent</a>  </p>
</blockquote>



<p>I have built a website with lots of functions supported by programming. As the website is growing bigger, I found when doing photo upload, login, the following errors appear:-</p>

<blockquote>
  <p>Warning: session_regenerate_id() [function.session-regenerate-id]: Cannot regenerate session id - headers already sent in /var/www/web92/web/li/sli.php on line 63</p>
  
  <p>Warning: Cannot modify header information - headers already sent by (output started at /var/www/web92/web/index826.php:62) in /var/www/web92/web/li/sli.php on line 72</p>
</blockquote>

<p>I found adding <code>ob_start();</code> at the very beginning of index can solve the problem, however, I would like to learn, if the running of php codes may have length limit.</p>
