Question

我试图检查用户名是否已在我的数据库中使用，但它没有回应任何内容（我运行时出现空白页），我想得到一个真或假的回复

<?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

您已使用mysqli_query和mysql_函数

进行了随机播放

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;
}

Answer 2

你正在混合mysql和mysqli：

所以你的问题只是一个错字，只需更改函数名称：

<?php

$link = mysqli_connect("localhost", "root", "password","data1"); 

if (!$link){
    // error handling goes here: mysqli_error()
}
$usercheck = "john";

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

$check = mysqli_query($link,"SELECT EXISTS(SELECT 1 FROM users WHERE username = $sanitizeduser) as check");
?>

同样要显示结果，您不能只使用echo $check，例如，您必须使用mysqli_fecth_array之类的内容。 See the manual

示例：

while($row = mysqli_fecth_array($check)) {
  echo $row["check"] . "<br>";
}

MYSQL查询错误 - 检查数据库中的用户

2 个答案: