Strange imagepng problems

Images & quot;) can be obtained, but the code cannot be displayed in the browser. it is always a red cross. this code can run normally on another machine. Is it my php configuration problem? & Lt ;? Strange question about header (& quot; Content-type imagepng
The code is as follows. it is strange that you can change imagepng ($ im) to imagepng ($ im, "kk.png") to get an image, but the image cannot be displayed in the browser, this code can run normally on another machine. Is it my php configuration problem?
Header ("Content-type: image/png ");
Srand (double) microtime () * 1000000 );
$ Login_check_number = strval (rand ("11111", "99999 "));
// $ Session-> setMember ("loginCheckNumber", $ login_check_number );

$ Im = imagecreate (50, 20) or die ("Cannot Initialize new GD image stream ");
$ Black = ImageColorAllocate ($ im, 9,142,204 );
$ ForeColor = ImageColorAllocate ($ im, 0, 0 );
$ White = ImageColorAllocate ($ im, 255,255,255 );
Imageline ($ instant, 1, 1,350, 25, $ black );
Imagearc ($ im, 200, 15, 20, 20, 35,190, $ white );
Imagestring ($ im, 5, 7, 3, $ login_check_number, $ white );
For ($ I = 0; $ I <100; $ I ++) // add interference pixels
{
Imagesetpixel ($ im, rand () % 50, rand () % 50, $ foreColor );
}

Imagepng ($ im );
Imagedestroy ($ im );
?>


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Discussion
Reference:
Reference:
If the GD library is not open, can imagepng ($ im, "kk.png" examples generate kk.png files?

It should be related to the browser.
Replace the first sentence with the header ("Content-type: image/x-png ");


I can't change it either.