Defer

Postpone the calling of a function or callable.

Why?

From Go by Example:

Defer is used to ensure that a function call is performed later in a program’s execution, usually for purposes of cleanup. defer is often used where e.g. ensure and finally would be used in other languages.

Common use cases are:

• Cleaning up temporary files.
• Closing network connections.
• Closing database connections.

Comparing defer to finally, this implementation of defer will allow us to have better control over when our deferred functions are called; we can decide when to start stacking deferred functions, and where to finally call them.

Examples

Usage

// Create an instance of Defer.
// When $defer falls out of scope, the deferred callables will be called in reverse order.
$defer = new Defer;

// Push your deferred tasks to the $defer object.
$defer->push(function () {
    echo "I'm echoed last!";
});

// As a convenience, you can also call $defer as a function
$defer(function () {
    echo "I'm echoed second!";
});

echo "I'm called first!";

Closing Resources

Defer can be used for ensuring the closing of open files:

$fp = fopen('/tmp/file', 'w');

$defer(function () use ($fp) {
   fclose($fp);
});

fwrite($fp, 'Some temporary data.');