Check to see if an email is already in the databas

问题:

I am trying to change my code to msqli prepared statements from mysql. I am not sure how to adapt my code that currently works to check if there is an email already in the database. Below is the code I am currently using that works. How do I change this into a prepared statement and get the same result?

//if email is equal to an email already in the database, display an error message

if(mysql_num_rows(mysql_query("SELECT * FROM users WHERE email = '".mysql_real_escape_string($_POST['email'])."'")))
{
  echo "<p class='red'>Email is already registered with us</p>";
} else {
  // missing code?
}

回答1:

Should be something like this:

// create mysqli object
$mysqli = new mysqli(/* fill in your connection info here */);

$email = $_POST['email']; // might want to validate and sanitize this first before passing to database...

// set query
$query = "SELECT COUNT(*) FROM users WHERE email = ?"

// prepare the query, bind the variable and execute
$stmt = $mysqli->prepare( $query );
$stmt->bind_param( 's', $email );
$stmt->execute()

// grab the result
$stmt->store_result();

// get the count
$numRows = $stmt->num_rows();

if( $numRows )
{
     echo "<p class='red'>Email is already registered with us</p>";
}
else
{
    // ....
}

This link may help you as well:

http://www.php.net/manual/en/mysqli.quickstart.prepared-statements.php