php代码禁止伪造数据提交

<?php

function CheckURL(){
    $servername=$_SERVER['SERVER_NAME']; 
    $sub_from=$_SERVER["HTTP_REFERER"]; 
    
    $sub_len=strlen($servername); 
    $checkfrom=substr($sub_from,7,$sub_len); 
    
    if($checkfrom!=$servername){
        die("非法提交,已拦截！"); 
    }
}

function createXHR(){

    if (window.XMLHttpRequest){
        var oHttp = new XMLHttpRequest();
        return oHttp;
    } else if (window.ActiveXObject){
        var versions = ["MSXML2.XmlHttp.6.0","MSXML2.XmlHttp.3.0"];
        for (var i = 0; i < versions.length; i++){
            try {
                var oHttp = new ActiveXObject(versions[i]);
                return oHttp;
            } catch (error) {
            
            }
        }
    }
    
    throw new Error("你的浏览器不支持AJAX！");
}


function ajaxPost(url,query_string=''){
    var hr = createXHR();
    hr.open('POST',url,false);
    
    hr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded; charset=gb2312");
    hr.onreadystatechange = function(){
        if (hr.readyState == 4)
            if (hr.status != 200)
                return;
    }
    hr.send(query_string);
}