Jasny · web development

I’m happy to say that many developers have found their way to Jasny Bootstrap. Especially the file upload component, is very popular. It can replace any normal <input type="file"> element to display a nice widget that is consistent across browsers and can show a preview for images.

This is just an image

The documentation shows the HTML to use, but it doesn’t show how to use it with existing files. I’ll explain it here.
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Turning links like www.example.com and http://twitter.com into clickable links. Sounds like an easy task, right? We’ll there are a few problems that might arise, especially if the text is already HTML formatted.

This function first takes out all potential dangers, by extracting links and tags and replacing them with a placeholder. It than extracts all URLs and replaces them with a placeholder, storing the full HTML link. At the end it replaces all placeholders with the links and tags.
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A backdoor provides access to an application bypassing the normal authentication process. There are many ways to do this. Some are more secure than others.

Why do you need a backdoor?

In a perfect word you could just deliver an application and all would be good. However in the real world there are unforeseen issues which need to be solved. This means that you as a developer will need access to the application. To reproduce the problem, you usually want to run the application logged in as the user that spotted the issue.

Another use of the backdoor is in a situation where you want to allow a user, that has already been authenticated, to bypassing further authentication. For example if you have a (web hosting) control panel where the user is already logged in, you can allow him to directly access the dashboard of the application without have to enter his password again. This requires a backdoor, since you don’t know his (unencrypted) password.
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In the article ‘Versioning MySQL data‘, I showed the basics of implementing a revisioning system using trigger. As Jens Schauder already pointed out, often the data of a record is spread across multiple tables, like an invoice with multiple invoice lines. Having each invoice line versioned individually isn’t really useful. Instead we want a new revision of the whole invoice on each change.
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As a developer you’re probably using a versioning control system, like subversion or git, to safeguard your data. Advantages of using a VCS are that you can walk to the individual changes for a document, see who made each change and revert back to specific revision if needed. These are features which would also be nice for data stored in a database. With the use of triggers we can implement versioning for data stored in a MySQL db.
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In the article ‘An alternative way of EAV modelling’, I discussed how to do EAV modelling by casting all values (except text) to integers. I’ll continue on that and talk about more advanced topics like multi-value fields.
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Officially PHP doesn’t support multiple inheritance. There are several ways around this, without having to duplicate code.

PHP 5.4 will support Traits. This concept is almost similar to mixins. For more information check the PHP manual.
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I’ve seen a lot of methods used to take a website temporarily off-line for maintenance. Most involve a using PHP to disable the site or renaming the index file. There is however a far better method of doing this, by placing the following in the vhost file or in an .htaccess file in the document root:

Header always set Retry-After "Thu, 18 Jun 2009 08:00:00 +0200"
Redirect 503 /

This way you are sure no part of the site is used. Also by returning a 503 http response, search-engine crawlers will not reindex your site right at the moment it is down. You can use ‘ErrorDocument’ to place a different text than the apache default.

Sun will be bought by Oracle. Will this be the beginning of the end of MySQL?

MySQL has a serious market share. For that oracle has already tried to buy MySQL back in 2006. In an interview responding to the offer in 2006, MySQL chief Marten Mickos told that the reason for declining was that they wanted to keep MySQL an independent product. From that I assume that oracle wanted to merge Oracle DB and MySQL technology. Even though MySQL will be part of a major merger for which the rules aren’t yet clear, you might think that Oracle hasn’t changed their ideas about what they want with MySQL in the last 3 years.

Won’t MySQL just lose most of its market share if it become something else. Other databases like PostgreSQL have been making mayor steps and are in many expects better than MySQL. MySQL has remained to be the only serious open-source RDBMS in respects of market share though. I believe this is mainly because MySQL is known, tried and tested. This might be a fragile thing though.

Based on Oracle’s decision, I might just take a more serious look at PostgreSQL. Changing is usually not so nice, but change often is.

Any thoughts? Leave a comment or trackback.

Associated websites often share user information, so a visitor only has to register once and can use that username and password for all sites. A good example for this is Google. You can use you google account for GMail, Blogger, iGoogle, google code, etc. This is nice, but it would be even nicer if logging in for GMail would mean I’m also logged in for the other websites. For that you need to implement single sign-on (SSO).

There are many single sign-on applications and protocols. Most of these are fairly complex. Applications often come with full user management solutions. This makes them difficult to integrate. Most solutions also don’t work well with AJAX, because redirection is used to let the visitor log in at the SSO server.

I’ve written a simple single sign-on solution (400 lines of code), which works by linking sessions. This solutions works for normal websites as well as AJAX sites.
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