Do SQL connections opened with PDO in PHP have to be closed

Manually closing(PDO breakup): When and why?

PHP's trash collector is quite efficient at cleaning up after the party(script ends), but there are specific scenarios where you might want to send your guests (PDO connections) home early:

• Long-running scripts: Because who wants guests hanging around all night?
• Resource-heavy scripts: You don't want your resources getting tired (nor do you want a noisy neighbour — the kernel — complaining).
• Daemon scripts: They hang around waiting for stuff to happen. Don't let them hog your DB connections.

The magic of garbage collection and reference counting

PHP’s reference counting and garbage collection mechanisms have a little magic up their sleeves. They work hand-in-hand to perform the clean-up:

• Every PDO object has its own charm(reference count).
• When charm drops to zero, the object is ready for garbage collection.
• Breaking the charm (unset variables or assign them null) brings the count down.

Scoping connections and persistence dilemmas

Limiting the scope and managing persistent connections properly is like having your cake and eating it too:

• Keep $dbh within a function or block so it's automatically forgotten when it goes out of fashion(scope).
• Configure destructors in classes to do your bidding and end connections once their job is done.
• Persistent connections are like in-laws; useful, but handle with care. They stay open across multiple scripts and can hog too many resources.

Active connection management: advanced users only!

On rare occasions, especially for the control freaks, you may want to intervene in the natural life cycle:

• Use SHOW PROCESSLIST in MySQL to keep an eye(output) on active connections. Be the big brother!
• Apply KILL command to end any problematic connection. Remember, with great power comes great responsibility!
• Note that this is like playing doctor; if you're not comfortable, let PHP handle it. It's pretty good at it.

Additional commandments to efficient PDO connection handling

Here are some golden rules(stern parent advice) for handling your PDO connections:

• Avoid persistent connections unless you're absolutely certain. They're not evil, just misunderstood.
• Encase your PDO usage within a class or a function so it gets cleaned up like clockwork.
• Keep an eye(monitor) on the connections your application spawns. Don't let them mutate into a resource-devouring monster!