$re = '/(?:<FONT[^>]*>|<\/FONT>)/m';
$str = '<UL><LI><FONT size=2 face=Verdana>random text<STRONG>random text</STRONG>random text<SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: \'Arial\',\'sans-serif\'; FONT-SIZE: 11pt; mso-fareast-font-family: \'Times New Roman\'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><SPAN style="mso-spacerun: yes"> </SPAN>random text</SPAN> </FONT></LI> <LI><FONT size=2 face=Verdana><FONT size=2 face=Verdana><STRONG>random text</STRONG></FONT></LI> <LI>random text</FONT></LI> <LI><FONT size=2 face=Verdana>random text</FONT></LI> <LI><FONT size=2 face=Verdana>random text</FONT></LI';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php