"Problem" Do picture verification code when garbled, in front of the header plus Ob_clean () can be magical display?!

The source code is as follows:

1<?PHP2    //Image Verification Code3 //The method must be at the top of the script4    Session_Start();5    //the correspondence between the verification code picture and the corresponding validation value6    $table=Array(7' Pic0 ' = ' bo ',8' Pic1 ' = ' hamster ',9' Pic2 ' = ' satsuma ',Ten' pic3 ' = ' Teddy ', One        ); A  -    $index=Rand(0,3); -      the    $value=$table[' pic '.$index]; -    //verification values for random CAPTCHA images -    $_session[' authcode '] =$value; -      +    //the address of the Verification code picture -    $filename=dirname(_file_). ' \\pic '.$index.‘. jpg; +    $contents=file_get_contents($filename); A     at    //The first picture does not display, displays a bunch of garbled characters, plus this sentence is good!  -    Ob_clean(); -  -    Header(' Content-type:image/jpeg '); -    Echo $contents; -  in?>

Check the document, it said, but I still do not know what it is talking about!

void ob_clean ( void )

This function is used to discard the contents of the output buffer.

This function does not destroy the output buffer, and the Ob_end_clean () function destroys the output buffer.

"Problem" to do the picture verification code garbled, in front of the header with Ob_clean () can be magical display?!