Several methods to obtain domain names in PHP

//Method 1 (using system variables)
//Disadvantages of not using the passed address and hosts that do not support system variables
echo $_SERVER[ 'HTTP_HOST'];
//Method 2 (use built-in function)
$url = 'http://www.51php.net/index.php?referer=51php.net' ;​​
$arr_url = parse_url($url); ​
echo $arr_url['host']; $url = str_replace('http://',",$url); //If there is an http prefix, remove it
 $pos = strpos($url,'/');
 if($pos === false )
　　{
　　　 return $url;
　　}else
　　lt;p>// Method 4 (using regular expressions)
preg_match("/^(http://)?([^/]+)/i", $url, $arr_domain);
echo $arr_domain[2];



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