Updated PDO and Abstraction Layer stuff.

_posts/06-01-01-Databases-and-PDO.md

@@ -1,6 +1,9 @@
 # Databases and PDO
 
-Many times your PHP code will use a database to persist information. If you use a database, use `PDO` to talk with it. PDO is a database abstraction library — (usually) built into PHP — that provides a common interface to talk with many different databases.
+Many times your PHP code will use a database to persist information. If you use a database, use `PDO` to talk with it. PDO is a 
+database connection abstraction library — built into PHP since 5.1.0 — that provides a common interface to talk with 
+many different databases. PDO will not translate your SQL queries or emulate missing features, it is purely for connecting to multiple 
+types of database with the same API.
 
 More importantly, `PDO` allows you to safely inject foreign input (e.g. IDs) into your SQL queries without worrying about database SQL injection attacks. This is possible using PDOStatements and bound parameters.
 
@@ -12,7 +15,8 @@ $pdo = new PDO('sqlite:users.db');
 $pdo->query("SELECT name FROM users WHERE id = " . $_GET['id']); // <-- NO!
 {% endhighlight %}
 
-This is terrible code. You are inserting a raw query parameter into a SQL query. This will get you hacked in a heartbeat. Instead, you should sanitize the ID input using PDO bound parameters.
+This is terrible code. You are inserting a raw query parameter into a SQL query. This will get you hacked in a heartbeat. Instead, 
+you should sanitize the ID input using PDO bound parameters.
 
 {% highlight php %}
 <?php
@@ -22,9 +26,20 @@ $stmt->bindParam(':id', filter_input(INPUT_GET, 'id', FILTER_SANITIZE_NUMBER_INT
 $stmt->execute();
 {% endhighlight %}
 
-This is correct code. It uses a bound parameter on a PDO statement. This escapes the foreign input ID before it is introduced to the database preventing potential SQL injection attacks.
+This is correct code. It uses a bound parameter on a PDO statement. This escapes the foreign input ID before it is introduced to the 
+database preventing potential SQL injection attacks.
 
 * [Learn about PDO][1]
+
+## Abstraction Layers
+
+Many frameworks provide their own abstraction layer which may or may not sit on top of PDO.  These will often emulate features for 
+one database system that another is missing form another by wrapping your queries in PHP methods, giving you actual database abstraction.
+This will of course add a little overhead, but if you are building a portable application that needs to work with MySQL, PostgreSQL and 
+SQLite then a little overhead will be worth it the sake of code cleanliness.
+
+Some abstraction layers have been built using the PSR-0 namespace standard so can be installed in any application you like:
+
 * [Doctrine2 DBAL][2]
 * [ZF2 Db][4]
 * [ZF1 Db][3]