This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
declare property as object?
in java you can create an object directly after the property field like this:
but it seems not working for php:
class Test {
public $object = new Object();
}
you have to create it in the __construct() and assign it to the property?
thanks
From php.net
This declaration may include an initialization, but this initialization must be a constant value--that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.
So no, you cant initialize it to an object. You'll have to do it in the constructor like you said
Related
This question already has answers here:
How can I call a static method from a class if all I have is a string of the class name?
(7 answers)
Closed 1 year ago.
I have the string with class name. I want to get a class with this name and call a static methods of this class.
How to make something like this?
$className = "Model";
getClassByName($className)::sayHello();
You can simply call the method on the variable, you might want to wrap an "if" around it to check if the class exists.
$className = "Model";
if (class_exists($className)) {
$className::sayHello();
}
You can check out this 3v4l for a repro case.
This question already has answers here:
PHP Error : Fatal error: Constant expression contains invalid operations
(5 answers)
Why I am suddenly getting a "Typed property must not be accessed before initialization" error when introducing properties type hints?
(2 answers)
Closed 2 years ago.
I have a class with typed property object. I need to define default empty value for that property:
This doesn't work:
public object $doctor = new \stdClass();
Is this even possible?
This is impossible and the error you get (Constant expression contains invalid operations) explains why: in PHP the properties can only be initialized with constant expressions. You can't use any function calls, variables or an expression producing a new object instance like in your case.
See more details here:
PHP Error : Fatal error: Constant expression contains invalid operations
As a workaround I'd suggest initializing the property in the constructor
Just declare a new class instance and fill
$ obj = new stdClass ();
public object $doctor = new stdClass();
$doctor->name="namedoctor"
$doctor->titles= array('doc', 'specialist');
This question already has answers here:
Static methods in PHP: what for?
(2 answers)
Closed 8 years ago.
I'm trying to figure out what static vars are.
They can be access without instantiating the class but what other benefits do they have and when should they be used?
For example, my class has a private var which holds the name of the twitter feed i'm trying to get.
Should this be static? It never needs to change.
Generally things which aren't instance specific but needs to be stored in a variable should be static variables. Otherwise this manual tells the details: http://php.net/manual/en/language.variables.scope.php
Otherwise you can consider using constants also. For the example you mentioned (as others wrote) using constants seems to be the most sensible. (Either a class constant, or simple one.)
Static variables are for when you want a variable inside a function to keep it's value if the function is called again.
An example of a static variable could be the following.
function addOne(){
static $i = 0;
$i++;
return $i;
}
echo addOne();
echo addOne();
echo addOne();
Which would return
123
Without the static keyword, this would simply return
111
In your question, you mention you have data that won't need to be changed. As the comments in the question state, you should make this a Constant.
In short, static variables can be used for constants.
For example, a Math class can have static variables; PI etc.
Let's say you have something in a class that you need later.
Now, you need that thing but you don't actually need|want|should create a new instance of that class.
That's why you use a static method/property
This question already has answers here:
In PHP, can you instantiate an object and call a method on the same line?
(9 answers)
Closed 8 years ago.
I've an object which returns a string and I would like instanciate another object with the string returned, why in PHP I can't instanciate this way ?
For Example:
// getController() returns a string name controller
$c = new $this->router->getController() ;
// I have to do this way:
$controller = $this->router->getController() ;
$c = new $controller() ;
Thank you for your help.
It's a syntax thing. I think I remember seeing an RFC to allow more dynamic class instantiation, but assigning to a variable first gets the job done, no?
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
what is the “::” notation in php used for?
I noticed this code while modifying a friends code and noticed this piece of code: TestPages::LoadMenu();
what does :: mean in php?
A great answer would mean a lot.
Thanks!
It's the 'Scope Resolution Operator'.
The Scope Resolution Operator (also called Paamayim Nekudotayim) or in
simpler terms, the double colon, is a token that allows access to
static, constant, and overridden properties or methods of a class.
http://php.net/manual/en/language.oop5.paamayim-nekudotayim.php
In layman terms it is used to call static Methods of a Class.
In your example, LoadMenu() is a static function of the TestPages class.
This means that you do not have to create an instance of a TestPages to call LoadMenu()
It is used to access static methods of class, static variables and constants
Read more
It means static class member access, in this case static method invocation.
It's used to access class methods / properties:
http://www.php.net/manual/en/language.oop5.paamayim-nekudotayim.php