Verification code garbled

I have written a verification code class for garbled verification codes. to help you find errors, I posted the class code in the encoding format gbk & lt ;? Phpheader (& quot; Content-type: image/png; charset = gbk & quot;); classCheckCode {private $ mCheckCodeNum = 4; pr verification code garbled
I wrote a verification code class. to help you find errors, I pasted the class code in the encoding format gbk.

Header ("Content-type: image/png; charset = gbk ");
Class CheckCode {
Private $ mCheckCodeNum = 4;
Private $ mCheckCode = '';
Private $ mCheckImage = '';
Private $ mDisturbColor = '';
Private $ mCheckImageWidth = '80 ';
Private $ mCheckImageHeight = '20 ';
Public function CreateCheckCode ()
{
$ This-> mCheckCode = strtoupper (substr (md5 (rand (), 0, $ this-> mCheckCodeNum ));
Return $ this-> mCheckCode;
}

Private function CreateImage ()
{
$ This-> mCheckImage = @ imagecreate ($ this-> mCheckImageWidth, $ this-> mCheckImageHeight );
Imagecolorallocate ($ this-> mCheckImage, 200,200,200 );
Return $ this-> mCheckImage;
}

Private function SetDisturbColor ()
{
For ($ I = 0; $ I <= 128; $ I ++)
{
$ This-> mDisturbColor = imagecolorallocate ($ this-> mCheckImage, rand (0,255), rand (0,255), rand (0,255 ));
Imagesetpixel ($ this-> mCheckImage, rand (2,128), rand (), $ this-> mDisturbColor );
}
}

Public function SetCheckImageWH ($ width, $ height)
{
If ($ width = ''| $ height ='') return false;
$ This-> mCheckImageWidth = $ width;
$ This-> mCheckImageHeight = $ height;
Return true;
}

Private function WriteCheckCodeToImage ()
{
For ($ I = 0; $ I <= $ this-> mCheckCodeNum; $ I ++)
{
$ Bg_color = imagecolorallocate ($ this-> mCheckImage, rand (0,255), rand (0,128), rand (0,255 ));
$ X = floor ($ this-> mCheckImageWidth/$ this-> mCheckCodeNum) * $ I;
$ Y = rand (0, $ this-> mCheckImageHeight-15 );
Imagechar ($ this-> mCheckImage, 5, $ x, $ y, $ this-> mCheckCode [$ I], $ bg_color );
}
}

Public function OutCheckImage ()
{
$ This-> CreateCheckCode ();
$ This-> CreateImage ();
$ This-> SetDisturbColor ();
$ This-> WriteCheckCodeToImage ();
Imagepng ($ this-> mCheckImage );
Imagedestroy ($ this-> mCheckImage );
}
}
?>

Define output in this page
$ C_check_code_image = new CheckCode ();
$ C_check_code_image-> OutCheckImage ();
All are completely normal. a verification code is displayed normally.
However, after I create a PHP page and add the include class, garbled characters will appear when I put the above two statements. the error code prompts Warning: cannot modify header information-headers already sent by (output started at E: \ www \ HSreport \ check_code.php: 1) in E: \ www \ HSreport \ class \ CheckCode. class. php on line 2
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------ Solution --------------------
The call page you created has a BOM header, which is output before header ().
Solution
------ Solution --------------------
Check whether the encoding of each page is the same, and whether there is an output statement before the header!