This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change in a future release of PHP without notice. Be warned and use this function at your own risk.
mb_output_handler() is ob_start() callback function. mb_output_handler() converts characters in output buffer from internal character encoding to HTTP output character encoding.
4.1.0 or later version, this hanlder adds charset HTTP header when following conditions are met:
Does not set Content-Type by header()
Default MIME type begins with text/
http_output setting is other than pass
contents : Output buffer contents
status : Output buffer status
Return Value: String converted
Note: If you want to output some binary data such as image from PHP script, you must set output encoding to "pass" using mb_http_output().
See also ob_start().