Untitled

<?php

/**
 * @return mysqli
 */
function dbConnect() {
    return mysqli_connect('local.dev', 'root', '123', 'test');
}

/**
 * @param string $error_text
 *
 * @return string
 */
function showError($error_text) {
    return <<<HTML
<p style="color: red; font-weight: bold">$error_text</p>
HTML;
}

/**
 * Return User ID using given username and password.
 * @param string $username
 * @param string $password
 *
 * @return int
 */
function getUserIdByUsernameAndPassword($username, $password) {
    $connection = dbConnect();
    // Filter vars
    $username = mysqli_real_escape_string($connection, $username);
    $password = mysqli_real_escape_string($connection, $password);

    // Create SQL query.
    $sql_query = <<<SQL
SELECT user_id FROM users WHERE email = '$username' AND psword = '$password'
SQL;
    // If it failed then something went wrong or user didn't exist
    $query = mysqli_query($connection, $sql_query);
    if (!$query) {
        return false;
    }
    $result = mysqli_fetch_assoc($query);

    return $result['user_id'];
}

/**
 * Get user by his/her id.
 * @param mysqli $connection
 * @param int $user_id
 *
 * @return array|bool|null
 */
function getUserById($connection, $user_id) {
    // Filter var
    $user_id = intval($user_id);

    // Create SQL query.
    $sql_query = <<<SQL
SELECT * FROM users WHERE user_id = '$user_id'
SQL;
    $query = mysqli_query($connection, $sql_query);
    if (!$query) {
        return false;
    }
    return mysqli_fetch_assoc($query);
}

/**
 * Update users table. Set $field_name = $field_value for a given $user_id
 *
 * @param mysqli $connection
 * @param string $field_name  Field name
 * @param string $field_value Field value
 * @param string $user_id     User ID
 *
 * @return bool
 */
function updateUserById($connection, $field_name, $field_value, $user_id) {
    // Filter values
    $field_value = mysqli_real_escape_string($connection, trim($field_value));
    $user_id = mysqli_real_escape_string($connection, trim($user_id));

    // Create SQL query
    $sql = "UPDATE users
                  SET `$field_name` = '$field_value'
                      WHERE user_id = '$user_id'";

    // Return result
    return mysqli_query($connection, $sql);
}

/**
 * Return auth form.
 * @return string
 */
function getAuthorizationForm()
{
    return <<<HTML
<form method="post" action="">
    <p>
     <input type="text" name="username">
    </p>
    <p>
      <input type="password" name="psword">
    </p>
    <p>
      <input type="submit" name="Login">
    </p>
</form>
HTML;
}