


Study, research and analysis of static keyword principle in PHP_PHP tutorial
看PHP手册的时候发现了下面这样一段代码:
function Test()
{
static $count = 0;
$count++;
echo $count;
if ($count < 10) {
Test();
}
$count--;
}
?>
执行结果如下:
这是一个递归的函数,声明的静态变量count记录次数,输出1~10。
我在看的时候有个疑惑,递归调用的时候 static $count = 0; 语句会重复执行,这为什么不会导致count变量被重复赋值呢?带着这个疑问和同事研究了一下,测试用代码如下:
echo 'start
';
static $a = 10;
echo "$a
";
unset($GLOBALS['a']);
echo "$a
";
static $a = 20;
echo "$a
";
$GLOBALS['a'] = 10;
echo "$a
";
static $a = 30;
echo "$a
";
unset($GLOBALS['a']);
echo "$a
";
static $a;
echo "$a
";
static $a = 40;
echo "$a
";
$a = 100;
echo "$a
";
static $a = 50;
echo "$a
";
static $a = 4;
echo "$a
";
echo 'end
';
exit;
?>
start
- 4
- Notice: Undefined variable: a
- 4
- 10
- 10
- Notice: Undefined variable: a
- 10
- 10
- 100
- 100
- 100
- end

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