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HomeBackend DevelopmentPHP Tutorial 关于上面这个递归,为什么最后的$a值为0?不是1吗

关于下面这个递归,为什么最后的$a值为0?不是1吗?

PHP code
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<?php echo Test ();
function Test() {
    static $a = 0;//这里是第4行
    echo $a . '<br>';
    $a ++;
    if ($a 


关于上面这个递归,为什么最后的$a值为0?不是1吗?
我用Debugger调试了下,发现运行顺序为:
顺序:4―5―6―7―8―4―5―6―7―10―11―10―11
$a值:0―0―1―1―1―1―1―2―2―1 ―1 ―0 ―0
最后运行输出的结果为
0
1
0
就是想问下,为什么10行和11行会运行两次?

谢谢了!

------解决方案--------------------
这样的执行循序
你说该之行几次
4 static $a = 0;//这里是第4行
5 echo $a . '
';
6 $a ++;
7 if ($a 8 Test ();
4 static $a = 0;//这里是第4行
5 echo $a . '
';
6 $a ++;
7 if ($a 9 }
10 $a --;
11 return $a;
9 }
10 $a --;
11 return $a;

------解决方案--------------------
PHP code

function Test() {
    static $a = 0;//这里是第4行 ------------------------(1)
    echo $a . '<br>';
    $a ++;
/*注意这里非注释代码的上下一行 ,return值必定是(1)处的定义*/
/*如果你想得到预期的返回结果1,
    if ($a 
                 
              
              
        
            
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