Update notification for a commercial plug-in

WordPress CMS has a nice auto update feature that displays update notifications for outdated plug-ins and themes in admin panel. Once you got a notification you can go to Dashboard->Updates and install all updates with few clicks while WordPress will automatically download and extract archives, remove old versions and reactivate plug-ins for you.

The only problem is  that it works for plug-ins published on wordpress.org which are open-source so it’s not an option for commercial plug-ins.

Luckily there is a very good solution to this problem: Upgrademe plug-in.
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Customers and users sometimes ask for an ability to save some reports from web applications to PDF files. It could be very tricky to write PDF directly but as far as you already have those reports on web pages you can add printable views of them and then ability to convert HTML/CSS of the pages to PDF, say with dompdf library.
This way you can hit two targets: add printing of reports and PDF export. Dompdf is still in beta but at least it could work on shared hosting AFAIK.

But what if you need to export web pages with JavaScript canvas elements like Flot charts that are plotted on browser side only? All available solutions require installing executables which is usually problematic on shared hosting.

The solution is PDFmyURL.com/ which you can easily use as a web-service: send GET requests with URL of the page you want to export and get PDF file as a response. The service is based wkhtmltopdf. As you can see, it’s good enough to convert pages with Flot charts:

http://pdfmyurl.com/?url=http://people.iola.dk/olau/flot/examples/basic.html.

You can call the service from JavaScript on your pages or from server-side scripts via any HTTP client library like cURL. All wkhtmltopdf options are supported and could be passed as GET request parameters.

Their free service inserts very small watermark to each page which is usually not a problem. But of course you can upgrade to paid service to remove it.

I use InnoDB storage engine because of support for transactions and referral integrity rules. However, MySQL still creates new tables as MyISAM by default. It was so annoying  to always define storage engine when creating new tables and double check that I didn’t forget it until I found how to set InnoDB by default.

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You may find the timestamp value returned by MySQL UNIX_TIMESTAMP() function 24 seconds grater than that returned by PHP functions and methods like strtotime(), mktime(), DateTime::getTimestamp(), Zend_Date::getTimestamp().

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Many many years ago I learned Delphi language. It has one interesting feature not found in other languages: you don’t need return statement to specify return value for a function. Instead, you can use a pseudo-variable called Result. You can change its value many times during function execution but only the last value is returned.

That’s really a great idea! Even if your programming language doesn’t have such a built-in variable, why not to create it?
Most functions actually need a variable to forge future return value, so why call it differently if we can always call it result?

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Perl-compatible regular expression functions in PHP can properly work with Unicode strings. Just add /u modifier to turn on UTF-8 support in preg_replace, preg_match, preg_match_all, preg_split and other PCRE (preg) functions. This way you can parse strings with national characters. For example:

$clean = preg_replace('/\s\s+/u', ' ', $dirty);

If used without /u modifier this code damages UTF-8 encoded strings by replacing national character bytes improperly interpreted as whitespace characters. This and many other problems are caused by improper interpretation of every byte as ASCII character which is not always true for UTF-8.

The modifier is available from PHP 4.1.0 or greater on Unix and from PHP 4.2.3 on win32. UTF-8 validity of the pattern is checked since PHP 4.3.5.
I found this tip as well as many other useful info on regular-expressions.info. It’s not easy to find it in the PHP documentation but it’s actually hidden here.

The Web community is going crazy about SEO-friendly URLs like http://somesite.com/products/network/router/. Well, it looks much better than a script URL http://somesite.com/products.php?c=network&p=router which may actually serve the page behind the scenes. There are a lot of good articles on how to implement SEO-friendly URLs, for example this one or my own post. But they do not warn the reader about one usual problem: once you have updated your site to handle virtual paths you will probably get a bad surprise:

CSS, image and internal page links are totally broken!

Why? Because those links are usually relative to the page location. The browser has no idea about virtual folders and tries to get files from locations relative to the page URL context. For example, if there is a usual CSS link in the page header:

<link rel="stylesheet" href="style.css" type="text/css" media="screen" />

Then the browser will try to download non-existing file http://somesite.com/products/network/router/style.css and fail silently. No CSS style will be applied.

It’s incredible how many words were spoken about SEO-friendly URLs with almost no word about this relative link problem.
So, what you have to do? Don’t worry, there are multiple solutions available and I’ll try to explain them all.

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