Above we have introduced to you the use of php recursive functions. I believe that friends have a certain understanding of the use of php recursive functions. So today we will introduce to you the implementation of php recursive functions. Three methods!
This article mainly introduces the three basic methods of implementing recursion in PHP, including using references as parameters, using global variables, and using static variables to implement recursion. It also attaches relevant examples and finally gives you a demonstration. , involving PHP's recursive operation skills, friends in need can refer to
Recursive functions are a type of function we commonly use. The most basic feature is that the function itself calls itself, but there must be ## before calling itself. #Conditional judgment, otherwise the call will continue indefinitely. What methods can be used to implement recursive functions? This article lists three basic ways. Understanding it requires a certain amount of basic knowledge, including an understanding of global variables, references, static variables, and an understanding of their scope. Recursive functions are also a good technique for solving infinite levels of classification. If you are interested in infinite classification, please refer to PHP to use recursive functions to achieve infinite classification. I'm used to explaining complex truths in layman's terms. If you really don't understand, please refer to the manual.
Using references as parameters
Regardless of whether references are used as parameters or not, we must first understand what a reference is? A reference simply means that two variables with different names point to the same storage address. Originally, each variable had its own storage address, and assignment and deletion went their own way. Okay now, the two variables share a storage address. $a=&$b; . What it actually means is that $a has to share the same room with $b regardless of its original storage address. Therefore any change to the stored address value will affect both values. Functions originally do their own thing, even if they are functions with the same name. Recursive functions consider taking references as parameters and becoming a bridge to form data sharing between two functions. Although the two functions seem to operate on different addresses, they actually operate on the same memory address.
function test($a=0,&$result=array()){
$a++;
if ($a<10) {
$result[]=$a;
test($a,$result);
}
echo $a;
return $result;
}Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 ) 。
Using global variables
Use global variables to complete recursive functions. Please make sure you understand what global variables are. The global variable declared within the function is just a reference to the external variable with the same name. The scope of the variable is still within the scope of this function. Changing the values of these variables will naturally change the values of external variables with the same name. But once & is used, the variable with the same name is no longer a reference with the same name. It is not necessary to understand such a deep level to use global variables to implement recursive functions. You can understand recursive functions naturally by maintaining the original view of global variables.function test($a=0,$result=array()){
global $result;
$a++;
if ($a<10) {
$result[]=$a;
test($a,$result);
}
return $result;
}Using static variables
We often see static in classes, and today we use it in recursive functions. Remember the role of static: initialize the variable only the first time the function is called, and retain the variable value. Give me an example:function test(){
static $count=0;
echo $count;
$count++;
}
test();
test();
test();
test();
test();function test($a=0){
static $result=array();
$a++;
if ($a<10) {
$result[]=$a;
test($a);
}
return $result;
}Summary
The so-called recursive function focuses on how to handle the function call itself and how to ensure that the required results can be reasonably "transmitted" between functions. Of course, there are also Recursive functions that need to transfer values between functions, for example:function test($a=0){
$a++;
if ($a<10) {
echo $a;
test($a);
}
}<?php
echo "<pre class="brush:php;toolbar:false">";
$area = array(
array('id'=>1,'area'=>'北京','pid'=>0),
array('id'=>2,'area'=>'广西','pid'=>0),
array('id'=>3,'area'=>'广东','pid'=>0),
array('id'=>4,'area'=>'福建','pid'=>0),
array('id'=>11,'area'=>'朝阳区','pid'=>1),
array('id'=>12,'area'=>'海淀区','pid'=>1),
array('id'=>21,'area'=>'南宁市','pid'=>2),
array('id'=>45,'area'=>'福州市','pid'=>4),
array('id'=>113,'area'=>'亚运村','pid'=>11),
array('id'=>115,'area'=>'奥运村','pid'=>11),
array('id'=>234,'area'=>'武鸣县','pid'=>21)
);
function t($arr,$pid=0,$lev=0){
static $list = array();
foreach($arr as $v){
if($v['pid']==$pid){
echo str_repeat(" ",$lev).$v['area']."<br />";
//这里输出，是为了看效果
$list[] = $v;
t($arr,$v['id'],$lev+1);
}
}
return $list;
}
$list = t($area);
echo "<hr >";
print_r($list);
?>Summary:
Three methods implement PHP recursive functions, which involve many PHP recursive operation skills. I hope it will be helpful to your work!related suggestion:
Examples of using php recursive functions
Do you know the precautions for using return in php recursive functions
What is PHP recursive function and simple example explanation
How to use PHP recursive function effectively? Typical examples of php recursive functions
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