Several precautions for using static methods in PHP, php static_PHP tutorial

A few things to note when using static methods in PHP, php static

The examples in this article introduce several common precautions when using static methods in PHP. Share it with everyone for your reference. The specific method is as follows:

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

2. The value of $this in a method called statically (using the :: operator) is determined by the context of the call! Not the class in which it is defined !!

For example, the following code:

<&#63;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
STATIC_V from TestClass1. The test found that I was actually wrong. The correct output is:

normal_v from TestClass2
STATIC_V from TestClass1

Note: 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 be a "bidirectional association".

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

Problems with static methods in php

self:: means calling the static method get() in this class; because only static methods can be called in static methods, and instance methods cannot be called. If you call instance methods, use this,

php static method calling problem

PHP can currently use two methods, static class, which is just for convenience of calling without initializing the class.
But if your writing is wrong. Static classes lose the ability to be called statically.
Give me an example of a mistake.

class Cat {
}
class Hypnotic_Cat extends Cat
{
public $string = "The cat was hypnotized.\r\n";
function Hypnotic_Cat()
{
}
public static function hypnotize()
{
echo self::$string;
}
}
Hypnotic_Cat ::hypnotize();
$hypnotic_cat = new Hypnotic_Cat();
$hypnotic_cat->hypnotize();
?>

Correct example

class Cat {
}
class Hypnotic_Cat extends Cat
{
public static $string = "The cat was hypnotized.\r\n";
function Hypnotic_Cat ()
{
}
public static function hypnotize()
{
echo self::$string;
}
}
Hypnotic_Cat::hypnotize() ;
$hypnotic_cat = new Hypnotic_Cat();
$hypnotic_cat->hypnotize();
?>

http://www.bkjia.com/PHPjc/879726.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/879726.htmlTechArticle Several things to note when using static methods in PHP, php static This article introduces several common ways to use static methods in PHP Things to note. Share it with everyone for your reference. The specific method is as follows:...