Detailed explanation of the differences between the two overloaded versions in PHP

"Overloading" is an implementation of polymorphism of the class. Function overloading means that an identifier is used as multiple function names, and these functions with the same name can be distinguished by the number of parameters or parameter types of the function, so that no confusion occurs when calling. The main advantage of this is that you don't have to write multiple functions for different parameter types or number of parameters.

Multiple functions use the same name, but the parameter list, that is, the number or (and) number of parameters

data type can be different. When calling, although the method name is the same, the parameter list is different depending on the parameters. The table can automatically call the corresponding function.
PHP4 only implements some of the simple functions of
Object-oriented, but the support for objects will be much more powerful in PHP5.
For polymorphic implementation, PHP4 only supports override but not overload. But we can use some tricks to "simulate" the implementation of overloading.

Although PHP5 can support overwriting and overloading, the specific implementation of overloading is quite different from other languages.

1, "simulate" overloading in PHP4

Try the following code:

<?php 
//根据参数个数选择执行不同的方法(在 PHP4 中模拟"重载"(多态的一种) 
class Myclass 
{ 
function Myclass() 
{ 
$method = "method" . func_num_args(); 
$this->$method(); 
} 
function method1($x) 
{ 
echo "method1"; 
} 
function method2($x, $y) 
{ 
echo &#39;method2&#39;; 
} 
} 
//通过在类中的额外的处理，使用这个类对用户是透明的： 
$obj1 = new Myclass(&#39;A&#39;); //将调用 method1 
$obj2 = new Myclass(&#39;B&#39;,&#39;C&#39;); //将调用 method2 
?>

In the above code, through the

constructor Use the func_num_args() function to get the number of parameters and automatically execute the method1 or method2 method. We can improve the above example by combining the functions func_get_arg(i) and func_get_args().
2, Use overloading in PHP5

First look at the following examples:

<?php 
class Myclass 
{ 
public $attriable; 
public $one = "this is one"; 
public $two = "this is two"; 
function construct() 
{ 
} 
function one($one) 
{ 
$this->one=$one; 
$this->attriable = $this->one; 
} 
function one($one, $two) 
{ 
$this->one=$one; 
$this->two=$two; 
$this->attriable = $this->one . $this->two; 
} 
function display() 
{ 
echo $this->attriable; 
} 
} 
$one = "this is my class"; 
$two = "Im the best"; 
$myclass = new myclass(); 
$myclass->one($one); 
$myclass->display(); 
$myclass->one($one, $two); 
$myclass->display(); 
//本例的做法，在 PHP 中是不正确的！ 
?>

People who have used overloading in C++, Java, and C#, It is very customary to write the PHP code for the above overloaded implementation. But this is not true in PHP5. PHP5 is not an imitation of the aforementioned languages, but has its own set of methods for implementing
method overloading (whether it is good or bad will not be discussed here). Although the classes of PHP5 are much more powerful than those of PHP4, the issue of "overloading" has not been "improved" as we expected. In "strongly" typed languages, "overloading" can be achieved through different parameter types, such as C++, Java, C#, etc. In languages ​​where "fixed parameters" are passed, it can also be passed by the number of parameters, such as Java, but PHP is a weakly typed language, so there will be no "overloading" like the above.
Overloading in PHP5 can be performed through several special methods: get, set, and call. PHP will call these methods when the Zend engine tries to access a member and cannot find it.

In the following example, get and set replace all accesses to the attribute variable array. If necessary, you can also implement any type of filtering you want. For example, a script can disable setting property values, start with a certain prefix, or include a certain type of value. The call method illustrates how you can call an undefined method. When you call an undefined method, the method name and the parameters received by the method will be passed to the call method, and PHP will return the call value to the undefined method.

<?php 
class Overloader 
{ 
private $properties = array(); 
function get($property_name) 
{ 
if(isset($this->properties[$property_name])) 
{ 
return($this->properties[$property_name]); 
} 
else 
{ 
return(NULL); 
} 
} 
function set($property_name, $value) 
{ 
$this->properties[$property_name] = $value; 
} 
public function call($method, $p) 
{ 
print("Invoking $method()<br>\n"); 
//print("Arguments: "); 
//print_r($args); 
if($method == &#39;display&#39;) 
{ 
if(is_object($p[0])) 
$this->displayObject($p[0]); 
else 
if(is_array($p[0])) 
$this->displayArray($p[0]); 
else 
$this->displayScalar($p[0]); 
} 
} 
public function displayObject($p) 
{ 
echo ("你传入的是个对象，内容如下:<br>"); 
print_r($p); 
echo "<hr>"; 
} 
public function displayArray($p) 
{ 
echo ("你传入的是个数组，内容如下:<br>"); 
print_r($p); 
echo "<hr>"; 
} 
public function displayScalar($p) 
{ 
echo ("你传入的是个单独变量，内容如下:<br>" . $p); 
echo "<hr>"; 
} 
} 
$o = new Overloader(); 
//调用 set() 给一个不存在的属性变量赋值 
$o->dynaProp = "Dynamic Content"; 
//调用 get() 
print($o->dynaProp . "<br>\n"); 
//调用 call() 
//$o->dynaMethod("Leon", "Zeev"); 
$o->display(array(1,2,3)); 
$o->display(&#39;Cat&#39;); 
?>

In the above code, the display() method is called, and the corresponding code segment in the class can be called according to the type and number of parameters, thus realizing the object method. Overload.

The above is the detailed content of Detailed explanation of the differences between the two overloaded versions in PHP. For more information, please follow other related articles on the PHP Chinese website!