Do not trust the reflection API

$output = ''; foreach (get_declared_classes() as $class) { $output .= $class . "\n"; $refClass = new ReflectionClass($class); foreach ($refClass->getMethods() as $method) { $output .= "\t" . $method->getName() . "()\n"; $params = $method->getParameters(); $output .= "\t\tParam count:" . count($params) . "\n"; foreach ($params as $param) { $output .= "\t\t$" . $param->getName() . "\n"; $output .= "\t\t\tisOptional(): " . var_export($param->isOptional(), true) . "\n"; $output .= "\t\t\tallowsNull(): " . var_export($param->allowsNull(), true) . "\n"; $output .= "\t\t\tisDefaultValueAvailable(): " . var_export($param->isDefaultValueAvailable(), true) . "\n"; if ($param->isDefaultValueAvailable()) { $output .= "\t\t\tgetDefaultValue(): " . var_export($param->getDefaultValue(), true) . "\n"; } else { $output .= "\t\t\tgetDefaultValue(): n/a\n"; } } } } echo $output;

According to the reflection API, none of the methods of XSLTProcessor takes any arguments:
XSLTProcessor importStylesheet() Param count:0 transformToDoc() Param count:0 transformToUri() Param count:0 transformToXml() Param count:0 setParameter() Param count:0 getParameter() Param count:0 removeParameter() Param count:0 hasExsltSupport() Param count:0 registerPHPFunctions() Param count:0
Well, the manual states otherwise.

Here is an example which contains wrong informations, it is from the PDOStatement class:
bindColumn() Param count:5 $column isOptional(): false allowsNull(): false isDefaultValueAvailable(): false getDefaultValue(): n/a $param isOptional(): false allowsNull(): false isDefaultValueAvailable(): false getDefaultValue(): n/a $type isOptional(): true allowsNull(): false isDefaultValueAvailable(): false getDefaultValue(): n/a $maxlen isOptional(): true allowsNull(): false isDefaultValueAvailable(): false getDefaultValue(): n/a $driverdata isOptional(): true allowsNull(): false isDefaultValueAvailable(): false getDefaultValue(): n/a

Three of five parameters here are optional. But they do not have a default value. (By the way, did you know about the last two parameters? They are not listed in the manual.) For comparison, here is the result of a user-defined class:
class OptionalParamTestClass { public function doSomething($foo, $bar = null) { return true; } }
OptionalParamTestClass doSomething() Param count: 2 $foo isOptional(): false allowsNull(): true isDefaultValueAvailable(): false getDefaultValue(): n/a $bar isOptional(): true allowsNull(): true isDefaultValueAvailable(): true getDefaultValue(): NULL

Not only is the allowsNull() return value completely different, while none of the internal class methods allow NULL on any of their parameters, its allowed for both in the user-defined class. Additionally the information about the default value is completely different for optional values.

I stumbled upon this when I tried to create a mock object of the PDOStatement class. The mock complained about missing parameters as the mock creation algorithm did not find any default values for some of the parameters. It took me some time to find that PDOStatement::bindColumn() has more parameters then stated in the manual, and that the reflection API outsmarted the mock creation algorithm about the optional parameters. The quick solution is to satisfy all parameters not required with NULL, but this does only work until the next optional parameter is added, and it renders optional parameters useless. The more stable solution is to check not only for default values of parameters in the mock creation code, but to explicitly ask if a parameter is optional and to use NULL as its default value. This solves the problem, but from my point of view it just does not sound right that reflection information is different for internal and user-defined classes.