Added exception doc

Author: C-Stevens

doc/exceptions-and-error-handling.md

@@ -0,0 +1,81 @@
+[<-- Return to index](../README.md)
+# Errors and Exception Handling
+
+### How are errors/exceptions treated?
+#### PHP
+Errors in PHP can be detected with a `try` block and a `catch` block. The code in the `try` block will be attempted and if any errors are encountered, the code in the `catch` block will execute. If there were no errors in the `try` code execution, the code in the `catch` block will be skipped.
+
+Exceptions can be thrown manually with the `throw` keyword. Since exceptions [are classes](https://secure.php.net/manual/en/class.exception.php) in PHP, you can still access all their inherited methods and properties.
+```php
+<?php
+function foo($bar) {
+	if($bar == "baz") {
+    	throw new Exception("Bar is equal to baz!");
+    }
+    return true;
+}
+
+try {
+	foo("baz");
+catch(Exception $e) {
+	print "An exception was caught: ".$e->getMessage();
+}
+?>
+```
+Will yield:
+```
+An exception was caught: Bar is equal to baz!
+```
+
+Custom exceptions can also be defined, since exceptions are objects:
+```php
+<?php
+	class myError extends Exception {
+    	public function reportError() {
+        	return "There was an error!";
+        }
+    }
+?>
+```
+#### Python
+Python differentiates between syntax errors and exceptions. Syntax errors raise at execution time and as one would expect only raise when there is invalid structure to the Python code.
+
+Exceptions are raised when an error is encountered at some point during code execution. Exceptions can be caught using the `except` keyword. in a `try` block. If the code in a `try` block encounters any error, the code in the `except` block will be executed. Otherwise, the code in the `except` block will be skipped.
+
+The `try` block can match a specific exception or catch all exceptions. If an exception is raised that is not handled by the `try` block, the exception will raise uncaught and terminate the program execution.
+
+```python
+>>> 10/0 // An uncaught exception
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+ZeroDivisionError: division by zero
+
+try:
+	10/0
+except ZeroDivisionError: // Catch only ZeroDivisionError exceptions
+	print("Divided by zero!")
+
+try:
+	10/0
+except: // Catch any exception thrown
+	print("Some exception was thrown!")
+```
+
+Exceptions can be manually thrown as well:
+```python
+>>>raise NameError
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+NameError
+```
+
+Python has many [built-in exceptions](https://docs.python.org/3/library/exceptions.html#bltin-exceptions), but you can also make your own by subclassing the `Exception` class:
+```python
+class myError(Exception):
+	pass
+
+>>>raise myError
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+  __main__.myError
+```