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Detailed explanation of the usage of php func_get_args and func_num_args functions

伊谢尔伦
伊谢尔伦Original
2017-07-08 11:16:151833browse

Friends who study PHP all know that PHP itself does not have functionsoverloading, let alone how to use it like java and c, but if we If you take a deeper look, you will find that you can use the func_get_args() and func_num_args() functions in PHP to implement function overloading. Here are two examples of function overloading. These two functions implement function overloading.

1. Default parameters. If this is not a required parameter in a function, and the corresponding default value is added, the corresponding function can be completed. The code is as follows:

The code is as follows:

function overloadFun($param1, $param2 = '1',$param3 = true)  
{  
 // do something   
}

Using the functions func_get_args() and call_user_func_array(), PHP code is as follows:

The code is as follows:

function rewrite() {     
$args = func_get_args();     
if(func_num_args() == 1) {     
func1($args[0]);     
} else if(func_num_args() == 2) {     
func2($args[0], $args[1]);     
}     
}     
    
function func1($arg) {     
echo $arg;     
}     
    
function func2($arg1, $arg2) {     
echo $arg1, ' ', $arg2;     
}     
    
rewrite('PHP'); //调用func1     
rewrite('PHP','China'); //调用func2


2, Use the default value to get the results you want based on the input. The code is as follows:

The code is as follows:

function test($name="小李",$age="23"){    
echo $name."  ".$age;    
}    
test();    
echo "<br/>";    
test("a");    
echo "<br/>";    
test("a","b");


3. Use call ($name, $arg) function is processed, the code is as follows:

The code is as follows:

<?php  
class OverLoad{  
function call($name, $args)  
{  
  if($name==&#39;overloadFun&#39;)  
  {  
   switch(count($args))  
   {  
    case 0: $this->overloadFun0();break;  
    case 1: $this->overloadFun1($args[0]); break;  
    case 2: $this->overloadFun2($args[0], $args[1]); break;  
    default: //do something  
      break;  
   }  
  }  
}  
     
function overloadFun0()  
{  
  echo 0;  
} 
function overloadFun1($var1)  
{  
  echo $var1;  
} 
function overloadFun2($var1,$var2)  
{  
    
  echo $var1+$var2;  
   }  
}    
$test=new OverLoad();  
$test->overloadFun()."<br />".   
$test->overloadFun(1)."<br />".   
$test->overloadFun(1,2)."<br />";  
?>

With such methods, we can use them to implement simple function overloading , but one thing to note is that as a weakly typed language, PHP itself cannot directly implement overloading like strongly typed languages ​​such as Java and C++. At least not now, we don’t know whether it will be available in future versions.

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