This function tries to return a string with all HTML and PHP tags
stripped from a given str. It uses
the same tag stripping state machine as the
fgetss() function.
You can use the optional second parameter to specify tags which
should not be stripped.
Note: allowable_tags was added in PHP 3.0.13
and PHP 4.0b3.
Since PHP 4.3.0, HTML comments are also stripped. This is hardcoded and can
not be changed with allowable_tags.
Warning
Because strip_tags() does not actually validate the
HTML, partial, or broken tags can result in the removal of more
text/data than expected.
Warning
This function does not modify any attributes on the tags that you allow
using allowable_tags, including the
style and onmouseover attributes
that a mischievous user may abuse when posting text that will be shown
to other users.