DMXZone.com has recently published an article of mine explaining how to parse RSS feeds using an open source PHP library called Magpie, and Ajax to handle the loading of the feeds. The feed reader is scalable to display as many or as few feeds as needed using an array to conveniently configure the script. If JavaScript is disabled or unavailable in the browser, the script gracefully degrades to offer a manual method of loading the feed headlines to the page rather than becoming disabled because of the Ajax calls that load them normally. Ajax is used in this example because fetching and parsing many feeds from many sources can result in an excessive page load delay as the script waits for all results to arrive. Using Ajax, you can display the headlines for each feed as they are received, resulting in an improved user experience.
You can take a look at the finished example, and download the code archive to see how it works.
When building content management systems, or most any web application, you often need to generate select menus dynamically by querying a database. A Select menu offers a user a set of predefined options to choose from, and prevent possible input errors that could occur if you instead gave the user a text field to type their selection, resulting in typos or selection of an option that is not available. A perfect example is when you have some list of categories stored in a table, and you need to create a form that allows a user to add a new record in a particular category. Here's what your table may look like:
A unique category Id is used as the primary key, creating a practical method of referencing a category. To query this table and generate a select menu, we can use a while loop like this:
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Notice that the select tags need to be written before and after the loop, so you don't end up with multiple menus, but just one menu
with many options. This approach is practical for future maintenance too, as you can simply add a new category to your database, and the interface will include it automatically.
The above example works great for building a menu on an add page where the user has not yet selected an option and stored it in a database,
but if you were creating an edit page you would need to have the user's previous selection already shown in the menu.to do this you would need to dynamically write in the selected="selected" attribute/value pair in the option tag for the category selected. Assume we have an articles table that has a CatID field that relates to our category table. To find out which option was selected we'll compare the CatID in the articles table and the CatID in the categories table as we run a loop to build the menu. We'll need to run two queries, one to get the articles record (in this demo I'll hard code in the id of the article we want) and one to get the categories.
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The $selected variable stores our attribute/value pair needed to preselect the user's option stored in the database, and will be empty if the condition was not met, thus leaving the option tag untouched.
Yet another common, dynamic select menu scenario is displaying date selections for years, months, or days. I create an external arrays file that has associative arrays of common lists such as this. Here is what such a file might look like. You could also add things like credit cards your e-commerce system accepts, and a list of countries for shipping information forms. Looping through associative arrays like this is a little different.
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