Description:
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The option 'default' does not seem to be documented anywhere in the "Types of filters" section (http://www.php.net/manual/en/filter.filters.php).

For example, the script below will return (int) 0 if 'id' doesn't exist or doesn't validate as INT.  This is not documented anywhere, which makes me wonder if there are other 'global' options like that.

Not sure where it should be documented though... Specific filter options are documented in "Validate filters" page (http://www.php.net/manual/en/filter.filters.validate.php).


Test script:
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var_dump(filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT, array('options' => array('default' => 0))));