php函数的传值与传址(引用)详解
在php中我们函数传值就比较简单了，但可能有些朋友地天真无邪函数传址或引用搞不明白，下面小编来给各位介绍在php中函数传值与传址(引用)介绍，希望对各位有所帮助。
php中引用的用法:
1. 变量的引用赋值: $a = &$b
2. 函数调用时的引用参数传递
1) 早期php是在调用时通过&符号传递引用类型的变量, 比如: func(&$arg);
2) 后来, 函数的引用类型参数被规定为需要在函数声明时定义, 不如: function func(&$arg);
注: 引用声明时定义引用类型参数后, 运行时引用参数传递被废弃, 需要在php.ini中增加allow_call_time_pass_reference来开启.
3. 函数返回引用类型, 这种应用方式需要声明函数时, 在函数名前增加&符号, 并且, 在调用时, 要用引用赋值方式, 比如:
| 代码如下 | 复制代码 |
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简而言之, 就是让函数的返回一个引用类型的值, 一个更实际的例子:
| 代码如下 | 复制代码 |
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$a = 1; |
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php函数传值的几个细节
| 代码如下 | 复制代码 |
| //一、基本数据类型的传值 /* **************************************************** */ function testvar($k){ $k = 40; } $c = 30; //给一个函数参数传一个基本数据类型(整型，布尔，字符 ...)， 实际上传的就是值 ; testvar($c); echo $c;//结果是：30 function testvar2(&$k){ $k = 40; } $e = 30; //给一个函数参数传一个基本数据类型(整型，布尔，字符 ...)， 实际上传的y就是地址 ; testvar2($e); echo $e;//结果是：40 /* **************************************************** */ //二、数组（默认情况下是复制一份数据），如要传地址则&$arr. $arr1 = array(-1,5,0); function testArr($arr){ for($i=0;$i $temp = $arr[$i]; $arr[$i] = $arr[$j]; $arr[$j] = $temp; } } } print_r($arr); //结果:Array ( [0] => -1 [1] => 0 [2] => 5 ) } testArr($arr1); print_r($arr1); //结果:Array ( [0] => -1 [1] => 5 [2] => 0 ) function testArr2(&$arr){ for($i=0;$i $temp = $arr[$i]; $arr[$i] = $arr[$j]; $arr[$j] = $temp; } } } } testArr($arr1); print_r($arr1); //结果:Array ( [0] => -1 [1] => 0 [2] => 5 ) /* **************************************************** */ //三、对象数据类型传值 class person{ public $name; public $age; } $a = new person(); $a->name = '小明'; $a->age = '20'; //变量a在存的是对象的地址，把a赋给b这个变量，实际上就是赋了一个地址。 $b = $a; $b->age = 30; //echo $a->age.$b->age;//结果是：30 30 //给一个函数参数传一个对象， 实际上传的是这个对象的地址; function test($k){ $k->age =40; } //调用 test($b); //echo $a->age.$b->age;//结果是：40 40 |
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php函数的传值与传址有什么区别呢？对于这样的问题我喜欢通过程序演示来获取答案。让我们来看一个演示记录吧！
| 代码如下 | 复制代码 |
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$i=100; function func($n){ $n=$n+100; return $n; } echo '1)函数传值前变量$i的值:'.$i.' '; echo '2)传值后函数的返回值:'.func($i).' '; echo '3)函数传值后变量$i的值:'.$i.' '; echo '4)函数传址前变量$i的值:'.$i.' '; echo '5)传址后函数的返回值:'.func(&$i).' '; echo '6)函数传址后变量$i的值:'.$i.' '; //echo func($i).' '; ?> |
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程序输出：
1)函数传值前变量$i的值:100
2)传值后函数的返回值:200
3)函数传值后变量$i的值:100
4)函数传址前变量$i的值:100
5)传址后函数的返回值:200
6)函数传址后变量$i的值:200
解释：
1)直接输出一个赋值$i=100的变量
2)func函数传值返回一个算术相加的结果$=100+100
3)func函数传值，其作用区域只限于函数内部，对外面的变量$i不会有影响
4)同上
5)func函数参数前多了个"&"符，表示传址，和2)一样，返回值是函数的算术运行结果。
6)func(&$i)，变量指针指向$i的位置，可以理解为是对变量$i的操作,$i=$i+100;这时变量$i已经相当于重新被赋值
如果去掉上面代码的第18行注释，会得什么结果呢？
小结：传址为了在执行函数的同时，同时改变函数参数值，而传值不期望改变。
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