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Added some information about Exceptions.
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_posts/03-03-01-Exceptions.md
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64
_posts/03-03-01-Exceptions.md
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---
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isChild: true
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---
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## Exceptions
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Exceptions are a standard part of most popular programming languages, but they are often overlooked by PHP programmers.
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Languages like Ruby are extremely Exception heavy, so whenever something goes wrong such as a HTTP request failing, or
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a DB query goes wrong, or even if an image asset could not be found, Ruby (or the gems being used) will throw an
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exception to the screen meaning you instantly know there is a mistake.
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PHP itself is fairly lax with this, and a call to `file_get_contents()` will usually just get you a `FALSE` and a warning.
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Many older PHP frameworks like CodeIgniter will just return a false, log a message to their proprietary logs and maybe
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let you use a method like `$this->upload->get_error()` to see what went wrong. The problem here is that you have to go
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looking for a mistake and check the docs to see what the error method is for this class, instead of having it made extremely
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obvious.
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Another problem is when classes automatically throw an error to the screen and exit the process. When you do this you
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stop another developer from being able to dynamically handle that error. Exceptions should be throw to make a developer aware
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of an error, then they can choose how to handle this. E.g:
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{% highlight php %}
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<?php
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$email = new Fuel\Email;
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$email->subject('My Subject');
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$email->body('How the heck are you?');
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$email->to('guy@example.com', 'Some Guy');
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try
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{
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$email->send();
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}
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catch(Fuel\Email\ValidationFailedException $e)
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{
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// The validation failed
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}
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catch(Fuel\Email\SendingFailedException $e)
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{
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// The driver could not send the email
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}
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{% endhighlight %}
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### SPL Exceptions
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An Exception by default has no meaning and the most common to give it meaning is by setting its name:
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{% highlight php %}
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<?php
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class ValidationException extends Exception {}
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{% endhighlight %}
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This means you can add multiple catch blocks and handle different Exceptions differently. This can lead to
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the creation of a <em>lot</em> of custom Exceptions, some of which could have been avoided using the SPL Exceptions
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provided in the [SPL extension][splext].
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If for example you use the `__call()` Magic Method and an invalid method is requested then instead of throwing a standard
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Exception which is vague, or creating a custom Exception just for that, you could just `throw new BadFunctionCallException;`.
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* [Read about Exceptions][exceptions]
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* [Read about SPL Exceptions][splexe]
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[exceptions]: http://php.net/manual/en/language.exceptions.php
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[splexe]: http://php.net/manual/en/spl.exceptions.php
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[splext]: /#standard_php_library
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@@ -11,7 +11,7 @@ CLI PHP programs are powerful because you can use your app's code directly witho
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Try running PHP from your command line:
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{% highlight bash %}
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> php -i
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php -i
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{% endhighlight %}
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The `-i` option will print your PHP configuration just like the [`phpinfo`][phpinfo] function. There are a number of other useful [command line options][cli-options], too.
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@@ -32,9 +32,9 @@ PHP sets up two special variables based on the arguments your script is run with
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To run our script, above, from the command line:
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{% highlight bash %}
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> php hello.php
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php hello.php
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Usage: php hello.php [name]
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> php hello.php world
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php hello.php world
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Hello, world
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{% endhighlight %}
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