How to use php recursive function effectively? Typical examples of php recursive functions

Regarding the usage of php recursive functions, share a few examples of phprecursive functions. In php programming, it is very common to use recursion to make function calls. Recursive functions can be used well to improve code efficiency. Learn through examples php recursion Function usage .

1. What is a recursive function?

A function calling itself within its function body is called a recursive call. This kind of function is called a recursive function.

What is the difference between recursive functions and non-recursive functions in php?

Example 1: Using static variables

Code example:

function test(){
    static $dig=0;
    if($dig++<10){
        echo $dig;
        test();
    }
}
test();//12345678910

Example 2: Using recursive functions and loops to reverse string arrangement

Code example:

function unreverse($str){
    for($i=1;$i<=strlen($str);$i++){
        echo substr($str,-$i,1);
    }
}
unreverse("abcdefg");//gfedaba
function reverse($str){
    if(strlen($str)>0){
        reverse(substr($str,1));
        echo substr($str,0,1);
        return;
    }
}
reverse("abcdefg");//gfedaba

2. PHP recursive function usage example

PHP recursive usage examples (php recursive function) include recursively obtaining the role ID string, recursively obtaining the cascade role information array, and obtaining child role information through the id of the parent role.

Example:

Code example:

//递归获得角色ID字符串
function explodeRole($roleObj, &$resultStr){
  if(0 < count($roleObj->childRoleObjArr)){
    foreach($roleObj->childRoleObjArr as $childRoleObj){
      if(&#39;&#39; == $resultStr){
        $resultStr .= "{$childRoleObj->id}";
      }else{
        $resultStr .= ", {$childRoleObj->id}";
      }
      explodeRole($childRoleObj, $resultStr);
    }
  }
}
 
//递归获取级联角色信息数组
function makeRoleRelation(&$roleObjArr){
  foreach($roleObjArr as $item){
    $item->childRoleObjArr = getRoleObjArrByParentId($item->id);
    if(0 < count($item->childRoleObjArr)){
      makeRoleRelation($item->childRoleObjArr);
    }
  }
}
 
//通过父角色的id获取子角色信息  
function getRoleObjArrByParentId($parentid){
  $operCOGPSTRTSysRole = new COGPSTRTSysRole();
  $operCOGPSTRTSysRole->setColumn($operCOGPSTRTSysRole->getAllColumn());
  $operCOGPSTRTSysRole->setWhere("parentroleid={$parentid}");
  $roleObjArr = $operCOGPSTRTSysRole->convResult2ObjArr($operCOGPSTRTSysRole->selectTable());
  return isset($roleObjArr)?$roleObjArr:array();
}

php recursive function usage

Example 1: Implement recursion using static variables.

Code example:

function test(){
  static $dig=0;
  if($dig++<10){
    echo $dig;
    test();
  }
}
test();//12345678910

Example 2: Use recursive functions and loops to reverse string arrangement.

Code example:

 function unreverse($str){ 
 for($i=1;$i<=strlen($str);$i++){ 
 echo substr($str,-$i,1); 
 } 
 } 
 unreverse("abcdefg");
 //gfedaba
 function reverse($str){ 
 if(strlen($str)>0){
 reverse(substr($str,1)); 
 echo substr($str,0,1); return; 
 } 
 } 
 reverse("abcdefg");//gfedaba

PHP recursive functions can sometimes be replaced by loops. It is recommended to use them when loops cannot be used instead, because loops are easier to understand and less prone to errors. PHP recursive functions PHP pays recursive functions. Recursive functions call themselves. These functions are particularly suitable for browsing dynamic data structures, such as trees and lists. Few web applications require the use of complex data structures.

Example:

Copy code Code example:

0) reverse_r(substr($str,1)); echo substr($str,0,1); return; } ?>

Two functions are implemented in this program listing. Both functions can print the contents of the string in reverse order. The function reversr_r is implemented through recursion, while the function reverse_i() is implemented through looping.

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