php数组函数排序之rsort() - 对数组的元素值进行降序排序

<?php
$my_array = array("a" => "Dog", "b" => "Cat", "c" => "Horse");
rsort($my_array);
print_r($my_array);
?>输出：

Array
(
[0] => Horse
[1] => Dog
[2] => Cat
)
Like sort(), rsort() assigns new keys for the elements in array. It will remove any existing keys you may have assigned, rather than just reordering the keys.  This means that it will destroy associative keys.

$animals = array("dog"=>"large",  "cat"=>"medium",  "mouse"=>"small");
print_r($animals);
//Array ( [dog] => large [cat] => medium [mouse] => small )

rsort($animals);
print_r($animals);
//Array ( [0] => small [1] => medium [2] => large )

Use KSORT() or KRSORT() to preserve associative keys.

<?php
$my_array = array("e" => "Dog", "b" => "Cat", "c" => "Horse");
ksort($my_array);
print_r($my_array);
?>输出：

Array(    [b] => Cat    [c] => Horse    [e] => Sog)

<?php 

error_reporting(E_ALL); 

class test{ 

public $public; 

private $private; 

protected $protected; 

static $instance; 

public function __construct(){ 

$this->public = 'public <br>'; 

$this->private = 'private <br>'; 

$this->protected = 'protected <br>'; 

} 

static function tank(){ 

if (!isset(self::$instance[get_class()])) 

{ 

$c = get_class(); 

self::$instance = new $c; 

} 

return self::$instance; 

} 

public function pub_function() { 

echo "you request public function<br>"; 

echo $this->public; 

echo $this->private; //private,内部可以调用 

echo $this->protected; //protected,内部可以调用 

$this->pri_function(); //private方法，内部可以调用 

$this->pro_function(); //protected方法，内部可以调用 

} 

protected function pro_function(){ 

echo "you request protected function<br>"; 

} 

private function pri_function(){ 

echo "you request private function<br>"; 

} 

} 

$test = test::tank(); 

echo $test->public; 

echo $test->private; //Fatal error: Cannot access private property test::$private 

echo $test->protected; //Fatal error: Cannot access protected property test::$protected 

$test->pub_function(); 

$test->pro_function(); //Fatal error: Call to protected method test::pro_function() from context 

$test->pri_function(); //Fatal error: Call to private method test::pri_function() from context 

?> 

<?php error_reporting(E_ALL);  class test{  public $public;  private $private;  protected $protected;  static $instance;  public  function __construct(){  $this->public    = 'public     <br>';  $this->private   = 'private    <br>';  $this->protected = 'protected  <br>';  }  static function tank(){  if (!isset(self::$instance[get_class()]))  {  $c = get_class();  self::$instance = new $c;  }   return self::$instance;  }       public function pub_function() {  echo "you request public function<br>";  echo $this->public;  echo $this->private;        //private,内部可以调用  echo $this->protected;      //protected,内部可以调用  $this->pri_function();      //private方法，内部可以调用  $this->pro_function();      //protected方法，内部可以调用  }  protected  function pro_function(){  echo "you request protected function<br>";  }  private function pri_function(){  echo "you request private function<br>";  } }  $test = test::tank(); echo $test->public; echo $test->private;    //Fatal error: Cannot access private property test::$private echo $test->protected;  //Fatal error: Cannot access protected property test::$protected $test->pub_function(); $test->pro_function();  //Fatal error: Call to protected method test::pro_function() from context $test->pri_function();  //Fatal error: Call to private method test::pri_function() from context  ?>

从上面的例子中，我们可以看出，
public: 可以class内部调用，可以实例化调用。
private: 可以class内部调用，实例化调用报错。
protected： 可以class内部调用，实例化调用报错。

<?php 

class test{ 

public $public; 

private $private; 

protected $protected; 

static $instance; 

public function __construct(){ 

$this->public = 'public <br>'; 

$this->private = 'private <br>'; 

$this->protected = 'protected <br>'; 

} 

protected function tank(){ //私有方法不能继承，换成public,protected 

if (!isset(self::$instance[get_class()])) 

{ 

$c = get_class(); 

self::$instance = new $c; 

} 

return self::$instance; 

} 

public function pub_function() { 

echo "you request public function<br>"; 

echo $this->public; 

} 

protected function pro_function(){ 

echo "you request protected function<br>"; 

echo $this->protected; 

} 

private function pri_function(){ 

echo "you request private function<br>"; 

echo $this->private; 

} 

} 

class test1 extends test{ 

public function __construct(){ 

parent::tank(); 

parent::__construct(); 

} 

public function tank(){ 

echo $this->public; 

echo $this->private; //Notice: Undefined property: test1::$private 

echo $this->protected; 

$this->pub_function(); 

$this->pro_function(); 

$this->pri_function(); //Fatal error: Call to private method test::pri_function() from context 'test1' 

} 

public function pro_extends_function(){ 

echo "you request extends_protected function<br>"; 

} 

public function pri_extends_function(){ 

echo "you request extends_private function<br>"; 

} 

} 

error_reporting(E_ALL); 

$test = new test1(); 

$test -> tank(); //子类和父类有相同名字的属性和方法，实例化子类时，子类的中的属性和方法会盖掉父类的。 

?> 

$a = "joe";
$b = "jerry";
if ($a != $b)
{
    echo "不相等";
}
else
{
    echo "相等";
}