Several considerations for using static methods in PHP

This paper introduces several common considerations for PHP to use static method. Share it for your reference. The specific methods are as follows:

1. Even if the method in the class is not declared with static, but it does not use changeable class member variables, it can still be called externally by the operator::;

2. The value of $this in a method called statically (using the:: operator) is determined by the context of the call! Instead of defining his class! !

For example, the following code:

<?php 
class TestClass1 
{ 
  public $normal_v = 'normal_v from TestClass1'; 
  public static $STATIC_V = 'STATIC_V from TestClass1'; 
  public function test_func1() 
  { 
    echo $this->normal_v.'<br />'.self::$STATIC_V; 
  } 
} 
class TestClass2 
{ 
  public $normal_v = 'normal_v from TestClass2'; 
  public static $STATIC_V = 'STATIC_V from TestClass2'; 
  public function test_func2() 
  { 
    TestClass1::test_func1(); 
  } 
} 
$t2 = new TestClass2(); 
$t2->test_func2(); 

What is the output of this code? I thought it would be normal_v from TestClass1 < br / > STATIC_V from TestClass1, the test found that I was wrong, and the correct output is:

normal_v from TestClass2
STATIC_V from TestClass1

Explanation: Although test_func1 () is defined in TestClass1, it is called in TestClass2, and its internal $this variable is determined by TestClass2!

In fact, the relationship between these two classes should belong to "two-way association".

Interested friends can test and run this example, and I believe there will be new gains!