The attached patch is by mike.

Same for ob_tidyhandler and ob_iconv_handler.
Found doing a grep php_output_handler_alias_register on source.

If that is considered correct behavior, which I'm personally fine with (but theoretically breaks backward compat), then there is one inconsistency with current implementation : ob aliases have higher precedence than userland function. That is edge case of course.

Consider:

<?php

function ob_iconv_handler($b)
{
  return $b . 'def';
}

ob_start('ob_iconv_handler'); // as I tested: this register the internal alias, not the above function

?>

This bug has been fixed in SVN.

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Thank you for the report, and for helping us make PHP better.