PHP prior to version 5.5 has no finally block - i.e., whereas in most sensible languages, you can do:
try {
//do something
} catch(Exception ex) {
//handle an error
} finally {
//clean up after yourself
}
PHP has no notion of a finally block.
Anyone have experience of solutions to this rather irritating hole in the language?
The RAII idiom offers a code-level stand-in for a finally block. Create a class that holds callable(s). In the destuctor, call the callable(s).
class Finally {
# could instead hold a single block
public $blocks = array();
function __construct($block) {
if (is_callable($block)) {
$this->blocks = func_get_args();
} elseif (is_array($block)) {
$this->blocks = $block;
} else {
# TODO: handle type error
}
}
function __destruct() {
foreach ($this->blocks as $block) {
if (is_callable($block)) {
call_user_func($block);
} else {
# TODO: handle type error.
}
}
}
}
Note that PHP doesn't have block scope for variables, so Finally won't kick in until the function exits or (in global scope) the shutdown sequence. For example, the following:
try {
echo "Creating global Finally.\n";
$finally = new Finally(function () {
echo "Global Finally finally run.\n";
});
throw new Exception;
} catch (Exception $exc) {}
class Foo {
function useTry() {
try {
$finally = new Finally(function () {
echo "Finally for method run.\n";
});
throw new Exception;
} catch (Exception $exc) {}
echo __METHOD__, " done.\n";
}
}
$foo = new Foo;
$foo->useTry();
echo "A whole bunch more work done by the script.\n";
will result in the output:
Creating global Finally. Foo::useTry done. Finally for method run. A whole bunch more work done by the script. Global Finally finally run.
PHP 5.3 closures can't access $this (fixed in 5.4), so you'll need an extra variable to access instance members with
If anyone is still keeping track of this question, you might be interested in checking out the (brand new) RFC for a finally language feature in the PHP wiki. The author already seems to have working patches, and I'm sure the proposal would benefit from other developers' feedback.