PHP 5.5 First Look
Illustration by Don Barnett

PHP 5.5 First Look

with Jon Peck

Video: Using "finally" with "try" and "catch"

One of the cooler features of object-oriented PHP is exceptions. An exception is a response to an abnormal event that typically requires the changing of the normal program execution flow. Up to this point, PHP has allowed code to try or attempt to do something. If an exception is thrown or created it can be caught, meaning handled gracefully. However, some program flows require some kind of closing operation that needs to happen even if there is an exceptional situation. Here's an example of pseudo code before PHP 5.5.

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Watch the Online Video Course PHP 5.5 First Look
42m 29s Intermediate Jun 14, 2013

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Join author Jon Peck as he demonstrates new functionality in PHP 5.5, including generators, the try-catch-finally execution model, and a brand-new password hashing API. A number of existing behaviors, such as the foreach() and empty() functions, have also been updated, and Jon explores what changed and how it can be used. Throughout this course, you'll learn to add new functionality to a simple deck of cards class using these new and updated features, and how to use them for the basis of your own project.

Topics include:
  • Using generators to create simple iterators
  • Dereferencing strings and arrays
  • Enhancing security with the password hashing API
  • Replacing APC with OPcache
  • Normalizing Boolean and unpack() behavior
  • Surveying the removed, incompatible, and deprecated functionality
Subject:
Developer
Software:
PHP
Author:
Jon Peck

Using "finally" with "try" and "catch"

One of the cooler features of object-oriented PHP is exceptions. An exception is a response to an abnormal event that typically requires the changing of the normal program execution flow. Up to this point, PHP has allowed code to try or attempt to do something. If an exception is thrown or created it can be caught, meaning handled gracefully. However, some program flows require some kind of closing operation that needs to happen even if there is an exceptional situation. Here's an example of pseudo code before PHP 5.5.

I'm going to lock database tables, attempt to write to the database, and then unlock the tables. If there's a problem, report the problem and unlock the tables. Notice that I have to manually unlock the tables in both steps. In PHP a new block is now available called Finally. Finally executes after a try/catch block and before normal execution resumes, which allows cleanup operation to run even if there's a problem. Here's how the same functionality would look in PHP 5.5, with less redundant code.

going to lock tables. Then try writing to the database. If there's a problem, I'll catch it. And finally, no matter what, I'll unlock the tables at the end. Let's see this in action. In NetBeans I'm navigate to pages > generate.inc.php. This is a page that will generate a 100 fictitious log entries of a non existent game. It starts off with a database connection which I put into exception mode. Then I lock the tables. So far, so good.

I start a try block, where I begin a transaction, prepare a statement, then loop through it 100 times. At the end of the loop, I commit, then unlock the tables. That's a lot of work in a single try block. After the try, There's a catch where if there's a problem I roll back the transaction, report that there was a problem and unlock the tables. To see this in action, let's go to the browser. Click on Generate. I'll see some Success and Info messages.

I'm going to look into the database to see the generated entries. Local host port 8080 and I'm going to go to PHP.myadmin, then I go to Sandbox and the log table. There's 100 total. Since these are random your rows may look a little different but you get the point. I'm going to switch back to the code and clean it up to make it more elegant. I'm going to add a finally block after the catch using the finally keyword. Finally. Either I'm going to unlock the tables.

So, unlock the tables. Database. Pdo. Exec. Unlock tables. And I'll show the success message there. I'm going to remove the unlocking from both the catch and the try, and save. I'm going to rerun the code in the browser, by clicking on generate again. Now when I got back to the table. And I can see that more entries were generated.

Going back to the application, click on log. This is going to render the log, for game one, with no security. Let's add a password to this process to only show the game log to somebody who has access.

Find answers to the most frequently asked questions about PHP 5.5 First Look .


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Q: How do I import the php55.sql file into MySQL?
A: Copy the php55.sql file from the Exercise Files folder to somewhere you can access it at the command line. (In this course, that's the 'sandbox' folder.)
 
Then type:
mysql -user=sandbox -password=sandbox sandbox < php55.sql
 
Be sure to substitute your MySQL username and password if necessary.
 
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