2012-12-19补充：

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写了一个测试了一下，很不错！

function parseHost($httpurl)

{

$httpurl = strtolower( trim($httpurl) );

if(empty($httpurl)) return ;

$regx1 = '/https?:\/\/(([^\/\?#]+\.)?([^\/\?#-\.]+\.)(com\.cn|org\.cn|net\.cn|com\.jp|co\.jp|com\.kr|com\.tw)(\:[0-9]+)?)/i';

$regx2 = '/https?:\/\/(([^\/\?#]+\.)?([^\/\?#-\.]+\.)(cn|com|org|net|cc|biz|hk|jp|kr|name|me|tw|la)(\:[0-9]+)?)/i';

$host = $tophost = '';

if(preg_match($regx1,$httpurl,$matches))

{

$host = $matches[1];

} elseif(preg_match($regx2, $httpurl, $matches)) {

$host = $matches[1];

}

if($matches) $tophost = $matches[2] == 'www.' ? $host:$matches[3].$matches[4].$matches[5];

return array($host,$tophost);

}

测试代码：

//test

$arr=array(

'http://www.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!',

'http://www.a.b.c.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!',

'http://www.a.b.c.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!',

'http://www.35dalu.com/#asdfasdfasd',

'www.35dalu.com',

'35dalu',

'http://a.b.c.d.com.cn:3306/asdfasdfadsfasd.asp?3adf=&adsfa#dead!dfadf^gadgad',

);

echo "

";

foreach ($arr as &$value) {

echo $value."\n";

print_r( parseHost($value));

echo "\n\n";

}

echo "

";

输出如下：

http://www.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!

Array

(

[0] => www.35dalu.com.cn:8080

[1] => www.35dalu.com.cn:8080

)

http://www.a.b.c.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!

Array

(

[0] => www.a.b.c.35dalu.com.cn:8080

[1] => 35dalu.com.cn:8080

)

http://www.a.b.c.35dalu.com.cn:8080/ABCDEFGH.PHP?A=1&B=2#0000!

Array

(

[0] => www.a.b.c.35dalu.com.cn:8080

[1] => 35dalu.com.cn:8080

)

http://www.35dalu.com/#asdfasdfasd

Array

(

[0] => www.35dalu.com

[1] => www.35dalu.com

)

www.35dalu.com

Array

(

[0] =>

[1] =>

)

35dalu

Array

(

[0] =>

[1] =>

)

http://a.b.c.d.com.cn:3306/asdfasdfadsfasd.asp?3adf=&adsfa#dead!dfadf^gadgad

Array

(

[0] => a.b.c.d.com.cn:3306

[1] => d.com.cn:3306

)