$mysqli_result && $mysqli_result->num_rows>0

這里老師寫的有錯誤，我翻了一下文檔做了糾正。記得給我采納最佳

<?php
$mysqli=new?mysqli('localhost','root','root','text');
if($mysqli->connect_errno){
	die($mysqli->connect_error);
}
$mysqli->set_charset('utf8');
$id=$_GET['id'];
$sql="SELECT?id,username,password,age?FROM?user?WHERE?id=".$id;
$mysqli_result=$mysqli->query($sql);
if($mysqli_result?&&?$mysqli_result->num_rows>0){
	$row=$mysqli_result->fetch_assoc();
}
//print_r($row);
?>