Regular expression to judge email and URL, please help me see if there is anything to add._PHP Tutorial

echo 'a:'.htmlspecialchars($a);
echo '
a1:';
$a1 = eregi_replace('(^[_.][:alnum:]-]+@([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}$)',' 1 ', $a) ;
echo htmlspecialchars($a1);
echo "
a1:$a1";
echo '
a2:';
$a2 = eregi_replace('([[:alnum:]]+://([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}([#?/][^#?/][:space:]][^[:space:]]*)?)',
        '1', $a);
echo htmlspecialchars($a2);
echo "
a2:$a2";
// eregi('^[_.][:alnum:]-]+@([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}$',$a) or die("not a email");
?>

    

http://www.bkjia.com/PHPjc/631878.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/631878.htmlTechArticlebodyonload=f.a.select(); ?php echo 'a:'.htmlspecialchars($a); echo 'bra1:'; $a1 = eregi_replace('(^[_.][:alnum:]-]+@([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}$)',' a href=mailto:1...