CODEgrunt blog

Sometimes reference documentation can do more to confuse than to help. Take the terms "URI" ("Uniform Resource Indicator") and "URL" ("Uniform Resource Locator"). You will often see these acronyms tossed around like they are radically different beasts and this can lead to confusion when sorting out what the authors intent is.

For those just wanting the quick answer, a URL is just a specific type of URI. They are not different things. Now for the long answer. . .

Back in ye olde days of the early World Wide Web there was a different view of how web pages (and other services) were going to be found. A URI represented the entire heirarchy of methods for finding resources and these were broken into 3 discrete types (with the option to add more later). The 3 types were URL, URN and URC (with the latter "Universal Resource Characteristic" never gaining common use). URLs were to be the addresses that machines would use to locate services and then there were URNs ("Universal Resource Name") which humans would use to find these services. The intent was that humans would never see URLs at all and much like how DNS maps human readable host names like "codegrunt.com" to numerical IP addresses, browsers would hide URLs behind more readable URNs using some external service to do the conversion between then.

Well, this approach never really took off as people (and programmers) started using URLs directly. While URNs still have a place in modern infrastructure, they are no longer thought of as a discrete type of URI. The W3C covers this pretty well:

URIs, URLs, and URNs: Clarifications and Recommendations 1.0

. . . according to the contemporary view, the term "URL" does not refer to a formal partition of URI space; rather, URL is a useful but informal concept: a URL is a type of URI that identifies a resource via a representation of its primary access mechanism (e.g., its network "location"), rather than by some other attributes it may have. Thus as we noted, "http:" is a URI scheme. An http URI is a URL. The phrase "URL scheme" is now used infrequently, usually to refer to some subclass of URI schemes which exclude URNs.

Unfortunately, even documentation writers do not always get the distinction fully right which does not help with the confusion of this issue:

PHP Documentation: parse_url()

Note: This function is intended specifically for the purpose of parsing URLs and not URIs. However, to comply with PHP's backwards compatibility requirements it makes an exception for the file:// scheme where triple slashes (file:///...) are allowed. For any other scheme this is invalid.

The above note suggests that URIs and URLs are not the same thing which is not true. What they should be saying is:

Note: This function is intended specifically for the purpose of parsing URI schemes "http" and for backwards compatibility reasons, "ftp".

Ah, jargon. How I hate love you.

topics: Internet, jargon, PHP

MySQL has come a long way since its early days what with stored query support and such. That said, the usage you will find in the average web application is still going to be limited to basic INSERT, UPDATE and SELECT queries. While there are no shortage of MySQL abstraction classes, all of the ones I have come across tend to either add too much overhead or do not really make the process of retrieving data from the backend any quicker or easier. Thus the creation of this MySQL handler class.

The intent with this class is not to be pretty or completist. It's goal is to provide the core functions needed for the average web application while keeping it simple. Query results are returned as multidimensional array using associative column names. It offers a few "magic" values by default ("insert_id" and "numrows") and has some utility functions thrown in for dealing with the result set.

I do not claim this is the most beautiful MySQL class out there. I can say however that it makes life a lot easier in many situations compared to either dealing with the database directly or using a full scale database abstraction layer.

A simple MySQL handler class.

topics: MySQL, PHP, programming

It is definitely not as commonly used these days but as a quick and dirty tool for non-critical applications, HTTP based authentication can still prove useful. The link that follows is for a PHP5 compatible HTTP authentication class I wrote a few years back. Specifics can be found in the source code.

A simple HTTP authentication class.

topics: programming, security

This code is pretty old now but still useful for basic checks against incoming credit card data. In most situations these days, this logic will be handled via supplied libraries from the processor themselves but it still is often useful to trim out the garbage data before you get to that point.

Source code for this simple credit card validation class can be found here.

topics: PHP, programming

I have added a new document discussing Javascript and bookmarks (it also acts as a landing page for those that click on the bookmark link with Javascript turned off).

adding a bookmark with Javascript

topics: javascript