Share the method of obtaining access IP in php

<?php                                                                 //方法1：
//方法4：
/**
 * 获取客户端IP地址
 * @param integer $type 返回类型 0 返回IP地址 1 返回IPV4地址数字
 * @return mixed
 */
function get_client_ip($type = 0) {
    $type       =  $type ? 1 : 0;
    static $ip  =   NULL;
    if ($ip !== NULL) return $ip[$type];
    if (isset($_SERVER[&#39;HTTP_X_FORWARDED_FOR&#39;])) {
        $arr    =   explode(&#39;,&#39;, $_SERVER[&#39;HTTP_X_FORWARDED_FOR&#39;]);
        $pos    =   array_search(&#39;unknown&#39;,$arr);
        if(false !== $pos) unset($arr[$pos]);
        $ip     =   trim($arr[0]);
    }elseif (isset($_SERVER[&#39;HTTP_CLIENT_IP&#39;])) {
        $ip     =   $_SERVER[&#39;HTTP_CLIENT_IP&#39;];
    }elseif (isset($_SERVER[&#39;REMOTE_ADDR&#39;])) {
        $ip     =   $_SERVER[&#39;REMOTE_ADDR&#39;];
    }
    // IP地址合法验证
    $long = sprintf("%u",ip2long($ip));
    $ip   = $long ? array($ip, $long) : array(&#39;0.0.0.0&#39;, 0);
    return $ip[$type];
}
echo get_client_ip();