为什么我从变量范围函数中获取额外值？

Question

任何人都可以解释为什么我使用以下脚本获取此输出

输出

1：第一 2第一 3first 4first 5第一 6第一 7first 8first 9首页 10first 10 9 8 7 6 五 4 3 2 1

function test() {
static $count = 0;
$count++;
echo $count."first";
echo "<br>";
if ($count < 10) {
    test();
}
echo $count--;
echo "<br>";
return $count."a"; }

Answer 1

十次案件太复杂而无法解释。在三次案例中，它更容易

1st test() => $count++; show '1first'; call next test();
2nd   test() => $count++; show '2first'; call next test()
3rd     test() => $count++; show '3first' $count--; show '3'; return
4th   $count--; show '2'; return
5th $count--; show '1'; return

编辑：

          call           call
test()  1  ->  test() 2  ->  test() 3
        1  <-         2  <-         3
          return        return

或

 test() 
 echo ++$count
 call ---------------> test() 
                       echo ++$count
                       call ---------------> test()
                                             echo ++$count
                                             echo $count--
                       echo $count-- <------ return
 echo $count-- <------ return
 return          

Answer 2

另外解释函数如何在堆栈环境中运行

先进先出

我只会在运行模式下对计数值进行评论＆lt; 3

// - First Call -
static $count = 0;
$count++; // count 1
echo $count."first"; // echo count 1first
echo "<br>"; 
if ($count < 3) {
    test();
}

// - Second Call -
static $count = 0; // ignore
$count++; // count 2
echo $count."first"; // echo count 2first
echo "<br>"; 
if ($count < 3) {
    test();
}

// - Third Call -
static $count = 0; // ignore
$count++; // count 3
echo $count."first"; // echo count 3first
echo "<br>"; 
if ($count < 3) {
    test(); // no more calling so we can continue to stack
}

// - Third Call Continues-
echo $count--; // echo count 3, count is now 2 
echo "<br>";
return $count."a";

// - Second Call Continues-
echo $count--; // echo count 2, count is now 1
echo "<br>";
return $count."a";

// - First Call Continues-
echo $count--; // echo count 1, count is now 0
echo "<br>";
return $count."a";