/**
 * 验证方法
 * @return bool
 */
function checkSignature(){
    $signature = $_GET["signature"];
    $tmpArr = [
        ‘timestamp‘ => $_GET["timestamp"],
        ‘nonce‘ => $_GET["nonce"],
        ‘token‘ => ‘xxx‘,
    ];
    sort($tmpArr);
    $tmpStr = implode( $tmpArr );
    $tmpStr = sha1( $tmpStr );

    if( $signature == $tmpStr ){
        return  $_GET[‘echostr‘];
    }else{
        return false;
    }
}

$res = checkSignature();
if($res){
    echo $res;
}