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web development tutorials

Monthly Archives: March 2011

mysql foreign key constraint

Posted on by Posted in PHP/mysql

#1005 – Can’t create table ‘tbl_user’ (errno:105)

While we design ER model of our database (schema) , we get this common error . i was asked by many of my friends and colleagues about this issue.
first we have to check the tables for both primary tables and foreign tables ,if a Er table exists we have to check for both main tables have primary key are indexed are not.

This error causes mainly adding foreign key constraint without indexing primary keys.
primary and foreign keys must have same type.
Another this works with only innoDB engine only.

htaccess hotlinker

Posted on by Posted in Html

How to stop hotlinking our web assets like images, music , video other files?

I recently i launched my project that will generates funny logo of user’s name , i worked around one week to complete this php script generates the funny logo. After one or two weeks users directly linking their logo to my hosting server ,than downloading and hosting on their server.This is called hotlinking where visitors will use directly from our hosted web assets.

So i want stop this hotlinking from hotlinker with htaccess , thanks to apache htaccess rewrite rules :) .

Here is my small tweak to my htaccess file that prevents hotlinking. 

RewriteEngine on
RewriteCond  %{HTTP_REFERER} !^$
RewriteCond  %{HTTP_REFERER} !^http(s)?://(www.)?maheshchari.com [NC]
RewriteRule  .(jpg|jpeg|png|gif)$ http://www.maheshchari.com/hotlink.jpg [NC,R,L]

In the above code snippet second and third lines are conditions , if the referrer is blank or maheshchari.com we allow images can be linked , if not we replace that images with hotlink.jpg image.

We can do this for not only images ,we can do it for other media files like mp3, video files, doc files also.

Remember:

You must replace the url to image or any doc file corresponding media type file.

You must allow some websites like facebook,google i.e famaous social networking sites, search engins.

for this you can add as many conditions you want like below

RewriteEngine On
RewriteCond %{HTTP_REFERER} ^http://(.+.)?google.com/ [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://(.+.)?yahoo.com/ [NC,OR]
RewriteCond %{HTTP_REFERER} ^http://(.+.)?technorati.com/ [NC]
 
with this method we can find the hotlinker also by redirecting to our mail sender php script the
referrer.

 

htaccess directory index

Posted on by Posted in Html

htaccess directory index

generelly when we access the directory on webserver, we get index.html or index.htm or default.asp or index.php.

in some situation we need to change the directory default page to other or specified page. We can set this with htaccess file on server . remember before going to view this tutorial , you have to check htaccess enabled by your web hosting provider.

open your favorite text editor and add following text to it and save as .htacces name . 

DirectoryIndex mydirectory.html

So when you open some url like

http://www.yoursite.com/directory/

you will serve the mydirectory.html as default page.

ping search engins

Posted on by Posted in PHP/mysql, seo

How to submit our new site to search engine.

Generelly web developers build sites or web application and think they completed their job, ofcourse it is. There is a little bit task is that submit the site to search engines like google,yahoo,bing and ask.Search engines will crawl the sites from TLD’s zone files in regular interval. So the main entry point for the site is index page of the site. from there search engines crawl the site,if the index page has proper linked. So if a page of our site to be submitted to search engine, it should be linked atleast on other pages. In most cases it won’t happen completely. In some cases our site or web application is complexed or user generated content.

So we should make a site map that has all site pages indexed in the specified format or protocal from the sitemap.org . We submit this sitemap.xml to search engines by ping . Even there is no use of sitemap.xml in the point of SEO (search engine optimisation) , but our site will be indexed properly .

Ping the search engines

Why we ping the search engins?

  • Search engine takes some time to crawl the web site depending on its schedule.
  • May be some web applications content is generated dynamically by users in timely manner .
  • In some cases our web site can not be properly inter linked to all our web pages.
  • improper navigation system.
  • Some content may be accessed by ajax only ,not for search engines.
  • Updating the web site content in regular interval, but search engine takes time to update that content.

What is sitemap.xml?

  • Sitemap is an easy way for webmasters to inform search engines about pages on their sites that are available for crawling. In its simplest form, a Sitemap is an XML file that lists URLs for a site along with additional metadata about each web page. You can see the detail protocal or format by visiting sitemaps.org

How to build sitemap.xml?

  • We can code the sitemap.xml if our web site is dynamically generated content.
  • We can build manually sitemap.xml ,if our site is static and has less pages.
  • We can build sitemap.xml by online tools,if our site is large and has more static pages.

How can we submit the sitemap.xml to search engins?

  • We can submit the sitemap.xml to search engine by manually in regular interval , weekly ,daily,monthly or when our web content is modified.
  • We can submit the sitemap.xml by scripting or coding with cron job with some regular interval or when our web content updated.

What are the submitting URLs of search engines?

Google: 

http://www.google.com/webmasters/sitemaps/ping?sitemap=http://www.yourwebsite.com/sitemap.xml

Yahoo: 

http://search.yahooapis.com/SiteExplorerService/V1/updateNotification?appid=YahooDemo&url=http://www.yourwebsite.com/sitemap.xml

MSN or Bing :

http://www.bing.com/webmaster/ping.aspx?siteMap=http://www.yourwebsite.com/sitemap.xml

Ask:

http://submissions.ask.com/ping?sitemap=http://www.yourwebsite.com/sitemap.xml

Ping the above serch engine submit urls

Just open your web browser address bar and copy the above URLS by replacing www.yourwebsite.com/sitemap.xml with your sitemap url.

Submitting sitemap with PHP

<?php
@file_get_contents("http://www.google.com/webmasters/sitemaps/ping?sitemap=http://www.yourwebsite.com/sitemap.xml");
@file_get_contents("http://search.yahooapis.com/SiteExplorerService/V1/updateNotification?appid=YahooDemo&url=http://www.yourwebsite.com/sitemap.xml");
@file_get_contents("http://submissions.ask.com/ping?sitemap=http://www.yourwebsite.com/sitemap.xml");
@file_get_contents("http://www.bing.com/webmaster/ping.aspx?siteMap=http://www.yourwebsite.com/sitemap.xml");
 
?>

Remember file_get_contents
function need permission for open remote pages on server, if not you can use fsocket_open, curl