How to use php recursive function effectively

This article explains the effective operations of PHP recursive functions.

Regarding the usage of PHP recursive functions, share a few examples of PHP recursive 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 PHP through examples. Use of recursive functions.

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 recursion Functions and loops implement string reversal arrangement

Code example:

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

2. PHP recursive function usage example

php recursive usage example (php recursive function), including recursive acquisition Role ID string, recursively obtain cascade role information array, obtain child role information through the id of the parent role.

Example:

//Recursively obtain the role ID string

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: Use static variables to implement recursion.

Code example:

function test(){ 
static $dig=0; 
if($dig++<10){ 
echo $dig; 
test(); 
} 
}
test();//12345678910   
例2：使用递归函数和循环实现字符串逆转排列。
代码示例:
function unreverse($str){ 
for($i=1;$i<=strlen($str);$i++){
echo substr($str,-$i,1);
}
}
unreverse("abcdefg");
//gfedcbc
function reverse($str){ 
if(strlen($str)>0){ 
reverse(substr($str,1)); 
echo substr($str,0,1); return;
} 
}
reverse("abcdefg");//gfedcbc

PHP recursive functions can sometimes be replaced by loops. It is recommended to use them when loops cannot be used, because it is easier for us to understand and less error-prone with loops. 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:

Code example:

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

This program list implements two functions, both of which can print the contents of a string in reverse order. The function reversr_r is It is implemented through recursion, and the function reverse_i() is implemented through loops.

This article explains the effective operation of recursive functions. For more related knowledge, please pay attention to the PHP Chinese website.

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