Converted chapters to markdown and changed pages to vertical layout

chapters/exceptions.md

@@ -0,0 +1,74 @@
+Sometimes things go wrong when someone uses your code. How do we handle this situation?
+PHP has Exceptions to define errors and the ability to "throw" them to stop code
+execution and tell the user of your code that something is wrong.
+```php
+<?php
+
+class Processor
+{
+    public function charge($creditCard)
+    {
+        if (strlen($creditCard->getNumber()) !== 16) {
+            throw new Exception('Credit card is not right');
+        }
+    }
+}
+```
+
+In this case, if someone tried to use the Processor class
+to charge a credit card number that is not 16 characters long, an
+exception will be thrown which stops the rest of the code from running.
+```php
+$processor = new Processor();
+$processor->charge('1234');
+```
+
+A developer who wants to prevent an exception from stopping code execution
+can catch the exception and use it for logging or display the error to a user.
+
+Just wrap the code that might throw an exception with the keyword "try" and brackets
+followed by "catch", the exception type in parentheses and more brackets.
+```php
+try {
+    $processor->charge('1234');
+} catch (Exception $e) {
+    echo $e->getMessage() . "\n";
+}
+```
+
+You can make your own custom exceptions as well. They are just classes
+that extend Exception.
+```php
+class MyCustomException extends Exception {}
+```
+
+Then, you can try to catch your exception instead of the base exception.
+```php
+try {
+    throw new MyCustomException('I am a custom exception');
+} catch (MyCustomException $e) {
+    echo "Cauth MyCustomException\n";
+}
+```
+
+Since all exceptions inherit from Exception, catching
+Exception will catch any and all exceptions that might be thrown.
+```php
+try {
+    throw new MyCustomException('I inherit from Exception');
+} catch (Exception $e) {
+    echo "Still caught MyCustomException\n";
+}
+```
+
+You can also create multiple catch blocks to handle different types of exceptions in
+one try-catch.
+```php
+try {
+    throw new MyCustomException('I am being thrown again');
+} catch (MyCustomException $e) {
+    echo "MyCustomException was caught\n";
+} catch (Exception $e) {
+    echo "Just in case a different exception is thrown\n";
+}
+```