How to Compare a String in an SQL Database to a PHP Variable

Question

Ok, so as the title says, I want to find out how I can compare a string in an SQL database to a PHP string.

<!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'"){

The line of code above is where I am trying to compare a value (from the column "username" in the table "accounts") in my SQL database to a string that the user entered to create an account ($makeAccount). This specific piece of code is suppose to tell the user if the username they are trying to set their for their account has already been taken.

However, everytime I run this code (and enter a username into the form that I can visually see in my database is not taken), it still says the username has already been taken, even though it's definetly not.

        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>

Thank you, all answers are appretiated. :)

P.S. This is the first program I am writing in PHP and the first time I am using an SQL database, so please, try to keep it simple, and understandable.

P.S.S I have tried many solutions, all with no success.

What do you expect of the if condition that holds some kind of query? — RST
– RST, Commented Nov 5, 2016 at 18:51
You can't just put the SQL in an if() statement. You need to call mysqli_query() to perform the database query, and mysqli_fetch_assoc() to get a row of results. This returns an associative array, and you can access the selected column values from it. The mysqli documentation has examples, and you should be able to find many tutorials on the web. — Barmar
– Barmar, Commented Nov 5, 2016 at 19:00

Ghostff · Accepted Answer · 2016-11-05 19:49:10Z

1

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

edited Nov 5, 2016 at 19:49

answered Nov 5, 2016 at 19:05

Ghostff

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2 Comments

Rick James Over a year ago

Do not suggest mixing mysql_* API calls with mysqli_* API calls. The former is deprecated and will not work with the latter.

Ghostff Over a year ago

@RickJames yeah mybad

HENOK MILLION · Accepted Answer · 2016-11-05 19:00:56Z

0

Please change the if statement of your comparison

from

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

to

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

answered Nov 5, 2016 at 19:00

HENOK MILLION

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