When we work as a freelance developer, either alone of with a multidisciplinary team, we can often find ourselves alone in our craft. It is easy to become isolated from the larger community of like developers, be they designers, web programmers, site owners, etc. Fortunately it can be just as easy to keep yourself a part of a community.

The twin functions htmlentities() and htmlspecialchars() both do the same basic job. You use them when you are displaying data, especially user input data, to:

• prevent the use of JavaScript for cross site scripting (XSS) attacks
• prevent the use of HTML that may otherwise break the page
• permit the display of special reserved HTML characters such as angle brackets

Try dropping a series of closing div or table tags in the middle of your page and you will see your layout break in creatively horrifying new ways.

I was recently presented with the need to select only values that are unique. Shortly after finishing I came across someone asking how to pick off unique entries using SQL. The task is complicated when you consider it in terms of logic but SQL provides the tools to make it surprisingly simple.

SELECT `column`
FROM `table`
GROUP BY `column`
HAVING (
COUNT( `column`) =1
) 

Let's say you were using the test data below:

One of the more useful tools in SQL especially for drawing up reports but by no means limited to this purpose, is the use of sub-queries and [NOT] EXISTS.

I commonly find IF NOT EXISTS used for INSERT statements to avoid overwriting existing data but this type of statement and use is very different.

You can determine if a value never occurs in a record set or you can very quickly and simply find out of a value does indeed occur.

To find if there are orphan products not assigned to a category: