Check that url already exsists in the database and outputting the exsisting created url

Question

I've created a script called spiralurl (tiny url script). I'm still learning and making changes as I go. One thing I can't get fixed is to check that the user entered url already exists in the database, if it does exist I want output to the user the already shorted url previously created.

Script is at: http://redspiral.net/spiralurl

Any help is much appreciated, I'm still a learner so... :).

Thanks.

Here is the code which I would edit I think.

<?php

/*

      Filename:  class_short_url.php
      Creation   Date: 18-03-2010     
      Author:    RedSpiral / Yogesh Nagarur
      URL:       www.redspiral.net  
      Project:   SpiralURL V2

*/



class ShortUrl
{
    /** set initial vars **/
    var $is_error;
    var $error_message;

    /** this function crates a new short url **/
    function create_url($long_url, $api = false)
    {
        /** set globals **/
        global $url, $_LANG, $_CONFIG;

        /** start sessions **/
        @session_start();

        /** set url var **/
        $this->long_url = $long_url;

        /** check url has http:// or https:// **/
        if(substr($this->long_url, 0, 7) != "http://"){ $this->long_url = 'http://'.$long_url; }

        /** check that $url var is not empty **/
        if(empty($this->long_url) || $this->long_url == '')
        {
            $this->is_error = 1;
            $this->error_message = '<div id="error">Please enter a url to shorten.</div>';
        }else

        /** check url is valid **/
        if(is_valid_url($this->long_url) == false)
        {
            $this->is_error = 1;
            $this->error_message = '<div id="error">Please enter a valid url.</div>';
        }else

        /** no error? **/
        if($this->is_error != 1)
        {
            /** generate new url id **/
            $this->short_url_id = rand_string(6, 30);

            /** insert link in to database **/
            @mysql_query("INSERT INTO short_urls (long_url, url_id, url_hits, owner, screenshot ) VALUES ( '".$this->long_url."', '".$this->short_url_id."', '0', '".$_SESSION['userid']."', '".$this->screenshot."')");

            /** show new url **/
            echo '<center><input id="link" readonly="readonly" onClick="this.select();" value="'.$url->url_base.'/'.$this->short_url_id.'" type="text"></center><div id="buttons"> <a id="copy" class="button" href="javascript:;"><img src="./assets/images/copy-icon.png" alt=""> Copy</a><a class="button" href="javascript:;" onClick="return addthis_open(this, \'more\', \''.$url->url_base . '/' .$this->short_url_id.'\', \''.$url->url_base . '/' .$this->short_url_id.'\')"><img src="./assets/images/share-icon.png" alt=""> Share</a></div></div>';

            /** exit **/
            exit();
        }
    }


    /** this function deletes a url **/
    function delete_url($url_id, $admin = false)
    {
        /** set globals **/
        global $url;

        /** start sessions **/
        @session_start();

        /** do delete **/
        if($admin == true):
        mysql_query("DELETE FROM short_urls WHERE url_id = '".$url_id."' LIMIT 1");
        else:
        mysql_query("DELETE FROM short_urls WHERE url_id = '".$url_id."' AND owner = '".$_SESSION['userid']."' LIMIT 1");
        endif;

        /** redirect **/
        if($admin == true): redirect($url->url_base.'/admin?manage_urls'); else: redirect($url->url_base.'/account/home'); endif;

        /** exit **/
        exit;
    }
}

?>

Answer 1

For Every URL you save, create an MD5 string (identifier) of that url and save it to the database. Next time a user enters the URL, you can check the md5 of entered URL against the MD5 in the database.

This will be faster than checking the url field of the database as it is a constant string length and you can make it a clustered index.