php - 检查用户名可用性 php

Question

<?php
$con = mysqli_connect('localhost','root','[mypassword]','dbhwsource');

if(isset($_GET['username'])){
$username = $con->real_escape_string($_GET['username']);
$test = $con->query("SELECT username FROM users WHERE username='$username'");
if($test!=false) die("usererror");
}

if(isset($_GET['email'])){
$email = $con->real_escape_string($_GET['email']);
$test = $con->query("select * from users where email='$email'");
if($test!=false) die("emailerror");
}

$con->close();
echo "ok";
?>

所以我只是想检查用户名/电子邮件是否可用，但无论输入的用户名是什么，我得到的只是“usererror”!我只是很沮丧，到处搜索示例代码，代码看起来没有任何问题。我做错了什么？

编辑:

$test = $test->fetch_assoc();
if(!empty($test)) die("usererror");

这成功了!

Answer 1

由于您的查询返回 true，这行 if($test!=false) die("usererror"); 被执行， 应该是这样的

$test = $con->query("SELECT username FROM users WHERE username='$username'");
$row_cnt = $test->num_rows;
if( $row_cnt > 0 ) { 
  //you already have user with this name, do something 
}