如何将SQL数据库中的字符串与PHP变量进行比较_Php_Mysql_Mysqli_Comparison

如何将SQL数据库中的字符串与PHP变量进行比较

php mysql

如何将SQL数据库中的字符串与PHP变量进行比较,php,mysql,mysqli,comparison,Php,Mysql,Mysqli,Comparison,好的，正如标题所说，我想了解如何将SQL数据库中的字符串与PHP字符串进行比较 <!DOCTYPE html> <html> <head> <title>Processing Request</title> <link rel="Stylesheet" href="style.css" type="text/css" /> </head> <body> <h1>Account Crea

好的，正如标题所说，我想了解如何将SQL数据库中的字符串与PHP字符串进行比较

<!DOCTYPE html>
<html>

<head>
<title>Processing Request</title>
<link rel="Stylesheet" href="style.css" type="text/css" />
</head>

<body>
<h1>Account Creation</h1>
    <h3>

    <?php
    $dbhost = "localhost";
    $username = "root";
    $password = "";
    $connect = mysqli_connect("$dbhost", "$username", "$password");
    $db = "accounts";

    if (!$connect){
        die("ERROR: Database connection failed: " . mysqli_connect_error());
    }

    mysqli_select_db($connect, $db);

    $makeUser = $_POST["makeUser"];
    $makePass = $_POST["makePass"];
    $sql = "INSERT INTO accounts (username, password) VALUES ('$makeUser', '$makePass')";


    if("SELECT username FROM accounts WHERE username = '$makeUser'"){


处理请求
帐户创建
请更改比较的if语句
从
到
您对保存某种查询的if
条件有何期望？您不能将SQL放在if（）
语句中。您需要调用mysqli\u query（）
执行数据库查询，调用mysqli\u fetch\u assoc（）
获取一行结果。这将返回一个关联数组，您可以从中访问选定的列值。mysqli文档中有一些示例，您应该可以在web上找到许多教程。不要建议将mysql\u*
API调用与mysqli\u*API调用混合使用。前者已被弃用，不能与后者一起使用。@RickJames yeah mybad
        header("Location: createaccount.php?status=userTaken");
    }
    else{
        mysqli_query($connect, $sql);
        echo "Account creation was succesful!";
    }

    mysqli_close($connect);
    ?>

    Click <a href="index.php">here</a> to login.

    </h3>
    </body>
</html>

if("SELECT username FROM accounts WHERE username = '$makeUser'"){

if(mysqli_query("SELECT username FROM accounts WHERE username = '$makeUser'")){

$sql = mysqli_query("SELECT username FROM accounts WHERE username = '$makeUser'");
if(mysqli_num_rows($sql) > 0)
{
   //exists
}
else
{
   //does not exist
}