error upload pic on the site bassed on Yii

if upload pic more 1mb, got error, php.ini have setting more 20mb upload_max. why?

POST site . com/file/file/upload/objectModel//objectId

500 Internal Server Error 20.67s jquery.min.js



<title>500 Internal Server Error</title>


<h1>Internal Server Error</h1>

<p>The server encountered an internal error or

misconfiguration and was unable to complete

your request.</p>

<p>Please contact the server administrator, and inform them of the time the error occurred,

and anything you might have done that may have

caused the error.</p>

<p>More information about this error may be available

in the server error log.</p>


<address>Apache/2.2.22 (Debian) Server at Port 80</address>


If you upload pic less 1mb, you got error too?

Its your apache you should check your error_log