PHP login function code Example of PHP implementing a simple login function

/**
* php login function
* edit: bbs.it-home.org
*/
// Remove unsafe html code for php and mysql.
function safestrip($string){
 $string = strip_tags($string);
 $string = mysql_real_escape_string($string);
 return $string;
}

//Login information display function
function messages() {
 $message = '';
 if($_SESSION['success'] != '') {
 $message = ''
 .$_SESSION['success'].'< ;/span>';
 $_SESSION['success'] = '';
 }
 if($_SESSION['error'] != '') {
 $message = ' .$_SESSION['error'].'';
 $_SESSION['error'] = '';
 }
 return $message;
}

// User login function
function login($username, $password){

//Filter the username and password entered by the user
$user = safestrip($username);
$pass = safestrip($password);

//Convert the password to md5 format
$pass = md5($pass);

 // Query whether the username and password in the database match
 $sql = mysql_query("SELECT * FROM user_table WHERE username = '$user'
 AND password = '$pass'") or die(mysql_error());

 //If = 1, the authentication is successful
 if (mysql_num_rows($sql) == 1) {

//Start recording in the session
$_SESSION['authorized'] = true;

// Reload the page
$_SESSION['success'] = 'Login successful';
header('Location: ./index.php');
exit;
} else {
// Login failure record In session
$_SESSION['error'] = 'Sorry, the username or password you entered is incorrect';
 }
}
?>