How to check if user already exists in MySQL with PHP

Question

I am using following code which is not working for me.

$con=mysqli_connect(\"localhost\",\"root\",\"\",\"my_db\");
$check=\"SELECT COUNT(*) FROM persons WHER         


        

Answer 1

You can try the following code:

$query_code = "SELECT COUNT(itemCode) FROM masterData WHERE itemCode='{$itemCode}'";
$result_login = mysqli_query($conn,$query_code);
$anything_found = mysqli_num_rows($result_login);

if($anything_found > 0) {
    $formOk = false;
    echo "ITEM CODE ALREADY EXISTS! Please try again.";  
}

Answer 2

this code works fine for you...

$con=mysqli_connect("localhost","root","","my_db");
$check="SELECT * FROM persons WHERE Email = '$_POST[eMailTxt]'";
$rs = mysqli_query($con,$check);
$data = mysqli_fetch_array($rs, MYSQLI_NUM);
if($data[0] > 1) {
    echo "User Already in Exists<br/>";
}

else
{
    $newUser="INSERT INTO persons(Email,FirstName,LastName,PassWord) values('$_POST[eMailTxt]','$_POST[NameTxt]','$_POST[LnameTxt]','$_POST[passWordTxt]')";
    if (mysqli_query($con,$newUser))
    {
        echo "You are now registered<br/>";
    }
    else
    {
        echo "Error adding user in database<br/>";
    }
}

Answer 3

mysqli_query returns a mysqli_result object. Rather than comparing this to an integer try using num_rows:

$res = mysqli_query($con,$check);
if($res->num_rows){
    //User exists
}

Edit: The above assumed the query was using SELECT * and this will not work with SELECT COUNT(*). Checkout Aleks G's answer.

Answer 4

mysqli_query function returns a resultset handle. You then need to read the rows from it:

$rs = mysqli_query($con,$check);
$data = mysqli_fetch_array($rs, MYSQLI_NUM);
if($data[0] > 1) {
    //user exists;
}

Also note that SELECT count(1) FROM ... will be faster than SELECT count(*) FROM ... You won't see much of a difference in a small table, but with a large table of several hundred thousand rows, the difference may be significant.