اجرا نشدن header

سلام
هنگام اجرای کد

header("Content-Type : image/png");

به این متن بر میخورم

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at postmaster@localhost to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

Apache/2.4.46 (Win64) OpenSSL/1.1.1j PHP/8.0.3 Server at localhost Port 80

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