正则表达式判断email和URL
<body
onload="f.a.select();"><?phpecho 'a:'.htmlspecialchars($a);echo '<br>a1:';$a1 = eregi_replace('(^[_.][:alnum:]-]+@([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}$)',' <a href="mailto:1">1</a> ', $a) ;echo htmlspecialchars($a1);echo "<br>a1:$a1";echo '<br>a2:';$a2 = eregi_replace('([[:alnum:]]+://([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}([#?/\][^#?/\][:space:]][^[:space:]]*)?)',
'<a href="1" target="_blank">1</a>', $a);echo htmlspecialchars($a2);echo "<br>a2:$a2";// eregi('^[_.][:alnum:]-]+@([[:alnum:]][[:alnum:]-]*.)+[[:alpha:]]{2,3}$',$a) or die("not a email");?><form name="f"><input
name="a" value="<?php echo $a; ?>"><input type="submit" ></form></body>