PHP引用传递与引用&一些用法介绍_PHP教程

function foo(&$var)
{
$var++;
}

$a=5;
foo($a);
echo $a;

// 输出的是：6

$a = 100; //声明变量a
$b = &$a; //声明变量b,引用自变量a
echo "$a
";
echo "$b
";
$a++; //变量a自增1
echo "$a
";
echo "$b
";//查看变量b,也增加了1,说明使用的是同一存储单元
?>

程序运行结果：

100
100
101
101

$a = 20;
$b = $a;
$a = $a + 10;
echo $a.' and '.$b;
?>

$a = 20;
$b = &$a;
$a = $a + 10;
echo $a.' and '.$b;
?>

view sourceprint?
1

2 $bar =& new fooclass();

3 $foo =& find_var($bar);

4 ?>

function foo(&$val1, $val2) {
$val1 += 1;
$val2 += 1;
}
$a=5;
$b=10;
foo($a,$b);
echo $a;
echo $b;
?>

$a = 1;
$b = &$a; //$a与$b指向同一内容
$b = 2;
echo $b; //2
echo $a; //2
传递引用
引用传递很简单，就是一个「&」符号，比如：

function foo(&$a) {
$a = 2;
}

$b = 1;
foo($b);
echo $b; //2

class foo {
public $value = 42;

public function &getValue() { // 需要一个"&"
return $this->value;
}
}

$obj = new foo;
$myValue = &$obj->getValue(); // 还需要一个"&"，$myValue是对class foo中的$value的引用
$obj->value = 2; // 修改对象的$value属性
echo $myValue; // 输出2，$myValue与class foo中的$value值相同

#include
int main(int argc, char const *argv[]) {
int a = 0;
int* b = &a;

printf("%in", a); //0
free(b);
printf("%in", a); //*** error for object 0x7fff6350da08: pointer being freed was not allocated
}

$a = new A;
$b = $a;
$b->testA = 2;

/*
* 此时$a,$b的关系：
* +-----------+ +-----------------+
* $a --> | object id | ---> | object(Class A) |
* +-----------+ +-----------------+
* ^
* +-----------+ |
* $b --> | object id | ---------+
* +-----------+
*
*
*/

$c = new B;
$a = $c;
$a->testB = "Changed Class B";

/*
* 此时$a,$b,$c的关系：
* +-----------+ +-----------------+
* $b --> | object id | ---> | object(Class A) |
* +-----------+ +-----------------+
*
* +------------+
* $a --> | object id2 | -------------+
* +------------+ |
* v
* +------------+ +-----------------+
* $c --> | object id2 | ---> | object(Class B) |
* +------------+ +-----------------+
*/

echo "object a: "; var_dump($a); //["testB"]=> string(15) "Changed Class B"
echo "object b: "; var_dump($b); //["testA"] => int(2)
echo "object c: "; var_dump($c); //["testB"]=> string(15) "Changed Class B"

$aa = new A;
$bb = &$aa; // 引用
$bb->testA = 2;

/*
* 此时$aa, $bb的关系：
*
* +-----------+ +-----------------+
* $bb --> | object id | ---> | object(Class A) |
* +-----------+ +-----------------+
* ^
* |
* $aa ---------+
*
*
*/

$cc = new B;
$aa = $cc;
$aa->testB = "Changed Class B";

/*
* 此时$aa, $bb, $cc的关系：
*
* +-----------+ +-----------------+
* | object id | ---> | object(Class A) |
* +-----------+ +-----------------+
*
* $bb ---->-----+
* |
* $aa ---->-----+
* |
* v
* +------------+
* | object id2 | --------------+
* +------------+ |
* v
* +------------+ +-----------------+
* $cc --> | object id2 | ---> | object(Class B) |
* +------------+ +-----------------+
*/

echo "object aa: "; var_dump($aa); //["testB"]=>string(15) "Changed Class B"
echo "object bb: "; var_dump($bb); //["testB"]=>string(15) "Changed Class B"
echo "object cc: "; var_dump($cc); //["testB"]=>string(15) "Changed Class B"