The solution :

if this error happens when you use include then header Be sure you use :

ob_start () at the most beginning of your code.

ob_start () :This function will turn output buffering on. While output buffering is active no output is sent from the script (other than headers), instead the output is stored in an internal buffer.

and ob_flush() at the bottom of your codes

ob_flush() : The buffer contents are discarded after this function is called.

Hope this info can help others who meet such a problem :)

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Ijajaja