A quick gotcha that I wasn't aware of, suppose you have a function definition like this:
<?php
function foo(array $bar = array('baz' => ''),$che){}
?>
And you want to check if $bar has a default value:
<?php
$rfunc = new ReflectionFunction('foo');
$rparams = $rfunc->getParams();
echo $rparams[0]->isDefaultValueAvailable() ? 'TRUE' : 'FALSE';
?>
That will echo 'FALSE' because $che has no default value so $bar becomes required and the Reflection interface no long sees $bar's default value of array('baz' => '').
The solution is to give $che a default value also:
<?php
function foo(array $bar = array('baz' => ''),$che = null){}
?>
And then $bar's default value will be visible again.
While I understand why it does this, I still wish there was a way to get the default value without resorting to giving all params after it a default value also.