YA: Login System Checks 20130602133558AAn5syI

<?php

// http://answers.yahoo.com/question/index?qid=20130602133558AAn5syI


session_start();

$server ="localhost";
$username ="root";
$password ="spenck23";
$database ="user_accounts";
$connect = mysqli_connect($server, $username, $password, $database) or die("cannot connect");

function __post($name){
    $var = ((isset($_POST[$name]))? trim($_POST[$name]) : '');
    return mysqli_real_escape_string( stripslashes( $var ) );
}

$username = __post('username');
$password = __post('password');


// Missing Closing Quotes (") on the statement below.
// Only return one column, saves resources.
// Matching the username and password in MySQL, frees you from doing the checks in PHP.
// LIMIT 1, stop searching once a match is found. No need to return multiple rows.
$result = mysqli_query($connect,"SELECT username FROM users WHERE username='$username' && password='$password' LIMIT 1");

if( !$result ){
    // Query Failed/Errored Display error message
    echo '<h3>MySQL Query Error</h3>';
    echo '<p>' . mysqli_error( $connect ) . '</p>';
    exit;
}else if( mysqli_num_rows( $result) === 1){ // One row returned = one match found
    // session_register() is depracated, stop using it.
    $_SESSION['username'] = $username;
    // Although no need to keep the password
    $_SESSION['password'] = $password;
    // header('location: login_success.php');
    // Why are you sending the user somewhere when there
    // is still data to display.
    echo '<p>Hello ' . $username . ', you have been logged in successfully.</p>';
}else{
    echo '<h3>Login Error</h3>';
    echo '<p>Username/Password combo is incorrect.</p>';
    exit;
}


// Tip: When PHP tells you the error is on one line, typically it is a line directly above that line
// or within a couple. I would suggest using a text editor with code highlighting. It will save you
// time looking for certain errors. ( http://notepad-plus-plus.org )

$result = mysqli_query($connect,"SELECT * FROM notes");

// Again Check if query was successfull.
if( !$result ){
    // Query Failed/Errored Display error message
    echo '<h3>MySQL Query Error</h3>';
    echo '<p>' . mysqli_error( $connect ) . '</p>';
    exit;
}else if( mysqli_num_rows( $result) === 0){ // Query Was successfull, but no notes to display
    echo '<h3>Query Successfull</h3>';
    echo '<p>There are currently no Notes in the database.</p>';
}else{ // Query Successful and at least one row of notes was returned.
    echo '<h3>Notes</h3>';
    while($row = mysqli_fetch_array($result)){
        echo $row['username'];
        echo "<br>";
    }
}

?>