The difference between static methods and static variables in PHP classes

About the usage of php static methods and static variables.

In PHP, there are two ways to access methods/variables of a class: 1. Create the object $object = new Class(), and then use "->" to call: $object->attribute/function, provided that the variable/method is accessible. 2. Directly call class methods/variables: class::attribute/function, whether static or non-static. But there are prerequisites: A. If it is a variable, the variable needs to be accessible. B. If it is a method, in addition to the method being accessible, it also needs to meet: b1) If it is a static method, there are no special conditions; b2) If it is a non-static method, it needs to be changed not to use $this in the method, that is, no non-static variables/methods are called. Of course, there is no problem in calling static variables/methods.

Let’s look at the difference between using $object->... and using class::...: 1. Using $object->..., you need to execute the constructor to create the object; 2. Use class::... to call static methods/variables without executing the constructor to create objects; 3. Use class::... to call non-static methods/variables, and there is no need to execute the constructor to create objects.

Since 2 and 3 are the same, what’s the point of static methods/variables existing? difference: 1. Static variables Static members only retain one variable value, and this variable value is valid for all instances, that is, all instances share this member. 2. Static method Static methods can be called directly using class::..., while non-static methods need to meet certain restrictions before they can be called using class::.. methods, as mentioned before.