I'm very new to PHP classes so forgive me if the answer is really obvious. I'm trying to figure out how to use a variable defined outside of a class inside of a class. Here is a very crude example
$myVar = 'value';
class myClass {
private $class_var = $myVar;
//REST OF CLASS BELOW
}
I know the above doesn't work, but how can I use the external $myVar inside the class?
Try this:
$myVar = 'value';
class myClass {
private $class_var;
public function __construct($myVar) {
$this->class_var=$myVar;
}
//REST OF CLASS BELOW
}
When declaring the class, you will need to pass $myVar like so, $myClass = new myClass($myVar);.
global is terrible practice. So please don't.
global it. DI is a strategy for a reason.
static keyword, and giving an object property an initial value is the responsibility of a constructor, as both your answer and DaveChen's show. I do agree that not mentioning global would be a mistake, but it should probably always come with a few caveats - for instance, as you say, that it could be a way of migrating older code that cannot trivially be de-globalised.Every function has its own "scope". You can override that by declaring a variable as global inside the function like this:
$myVar = 'value';
class myClass {
public function __construct() {
global $myVar;
$this->class_var=$myVar;
}
}
this will set variable in the object instance.
However be advised that you can directly use it in functions without the need to set it as class variable like this:
$myVar = 'value';
class myClass {
public function myfunction() {
global $myVar;
echo $myVar;
}
}
global is constrained to the constructor, you are limiting the number of references to that global variable, and it can even be migrated to DI at some point in the future.