functions.php

<?php

// provide some SQL injection protection by sanitizing any variables
function sanitize($var)
{
    $var = trim($var);
    $var = htmlspecialchars($var, ENT_QUOTES);
    return $var;
}

// function for creating the random string for the unique url
function generate_code()
{

    // create the charset for the codes and jumble it all up
    $charset = str_shuffle(CHARSET);
    $code = substr($charset, 0, URL_LENGTH);

    // verify the code is not taken
    while (count_urls($code) > 0)
        $code = substr($charset, 0, URL_LENGTH);

    // return a randomized code of the desired length
    return $code;
}


// function to count the total number of short urls saved on the site
function count_urls($code = '')
{

    // build the extra query string to seach for a code in the database
    if ($code != '')
        $extra_query = " WHERE code='$code'";
    else
        $extra_query = "";

    // connect to the database
    $conn = mysqli_connect(DB_SERVER, DB_USER, DB_PASS, DB_NAME);

    // count ow many total shortened urls have been made in the database and return it
    $count = (int) mysqli_num_rows(mysqli_query($conn, "SELECT * FROM short_links " . $extra_query));
    return $count;
}

// function to perform all the validation needed for the urls provided
function validate_url($url)
{
    // make sure the user isn't trying to shorten one of our urls
    if (substr($url, 0, strlen(SITE_ADDR)) != SITE_ADDR) {
        return filter_var($url, FILTER_VALIDATE_URL);
    } else
        return false;
}