php - MYSQL查询错误-检查数据库中的用户

Question

我试图检查用户名是否已在我的数据库中使用，但它没有回显任何内容(当我运行时为空白页)，我想得到一个真或假的响应

<?php

 mysql_connect("localhost", "root", "") or die(mysql_error()); 

 mysql_select_db("data1") or die(mysql_error()); 


$usercheck = "john";

    $sanitizeduser= filter_var($usercheck, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW);

    $check = mysql_query("SELECT EXISTS(SELECT 1 FROM users WHERE username = $sanitizeduser)");

    echo $check;

?>

Answer 1

你已经使用了 mysqli_query 和 mysql_ 函数

试试这个，

$link = mysqli_connect("localhost","root","","data1") or die("Error " . mysqli_error($link));
$usercheck = "john";

$sanitizeduser= filter_var($usercheck, FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW);

$result = $link->query("SELECT username FROM users WHERE username = '".$sanitizeduser."' ");

$row_cnt = $result->num_rows;    
if($row_cnt>0){     
    echo "User Exists"; // echo 1;
}else{      
    echo "No User found"; //echo 0;
}