How do i detect of a certain class has constructor method in it? eg:
function __construct()
{
}
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I think __construct is PHP5 syntax, not? Maybe the tags should be corrected then (removal of php4)ChristopheD– ChristopheD2009-12-09 07:08:06 +00:00Commented Dec 9, 2009 at 7:08
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1Why do you need to know? it does not affect the ability to make a new instance. You could always consult the PHPDocs.Don– Don2009-12-09 07:10:56 +00:00Commented Dec 9, 2009 at 7:10
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but if the method is in fact private it does affect this ability, but then i don't know how to check it.Peter Lindqvist– Peter Lindqvist2009-12-09 07:13:23 +00:00Commented Dec 9, 2009 at 7:13
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Or the example be changed to reflect php4 behaviourPeter Lindqvist– Peter Lindqvist2009-12-09 07:46:31 +00:00Commented Dec 9, 2009 at 7:46
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4 Answers
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function hasPublicConstructor($class) {
try {
$m = new ReflectionMethod($class, $class);
if ($m->isPublic()) {
return true;
}
}
catch (ReflectionException $e) {
}
try {
$m = new ReflectionMethod($class,'__construct');
if ($m->isPublic()) {
return true;
}
}
catch (ReflectionException $e) {
}
return false;
}
Using method_exists() can have it's pros, but consider this code
class g {
protected function __construct() {
}
public static function create() {
return new self;
}
}
$g = g::create();
if (method_exists($g,'__construct')) {
echo "g has constructor\n";
}
$g = new g;
This will output "g has constructor" and also result in a fatal error when creating a new instance of g. So the sole existance of a constructor does not necessarily mean that you will be able to create a new instance of it. The create function could of course return the same instance every time (thus making it a singleton).
Comments
There's a couple ways, and it sort of depends on exactly what you're looking for.
method_exists() will tell you if a method has been declared for that class. However, that doesn't necessarily mean that the method is callable... it could be protected/private. Singletons often use private constructors.
If that's a problem, you can use get_class_methods(), and check the result for either "__construct" (PHP 5 style) or the name of the class (PHP 4 style), as get_class_methods only returns methods that can be called from the current context.
Comments
Reflection API expose isInstantiable()
$reflectionClass = new ReflectionClass($class);
echo "Is $class instantiable? ";
var_dump($reflectionClass->IsInstantiable());
Comments
