php自定义函数间的值传递/引用传递用法详解

1.值传递

<?php 
function exam($var1){ 
$var1++； 
echo
 "In Exam:" . $var1 . "<br />"; 
} 
$var1 = 1; 
echo $var1 . "<br />"; 
exam($var1); 
echo $var1 . "<br />"; 
?>

-------------------------------------------------------------------------------
输出结果：
1
In Exam: 2
1
-------------------------------------------------------------------------------
2.引用传递

<?php 
function exam( &$var1){ 
$var1++； 
echo "In Exam:" . $var1 . "<br />"; 
} 
$var1 = 1; 
echo $var1 . "<br />"; 
exam($var1); 
echo $var1 . "<br />"; 
?>

-------------------------------------------------------------------------------
输出结果：
1
In Exam: 2
2
-------------------------------------------------------------------------------
3.可选参数

function values($price, $tax=""){ 
$price += $prive * $tax; 
echo "Total Price:" . $price . "<br />"; 
} 
values(100, 0.25); 
values(100);

输出结果：
Total Price: 125
Total Price: 100
-------------------------------------------------------------------------------
4.如果传入的是一个对象，可以更改该对象的值
（实际上变量$obj记录的是这个对象的句柄，将$obj作为参数传入，完全可以对原对象进行操作。）

<?php 
class
 Obj{ 
public $name; 
public $age; 
public $gander; 
public function construct($name, $age, $gander){ 
$this->name = $name; 
$this->age = $age; 
$this->gander = $gander; 
} 
public function show_info(){ 
echo $this->name . " " . $this->age . " " . $this->gander . "<br />"; 
} 
} 
function grow($obj){ 
$obj->age++; 
} 
function test(){ 
$obj = new Obj("Mr. zhan", "12", "male"); 
$obj->show_info(); 
grow($obj); 
$obj->show_info(); 
grow($obj); 
$obj->show_info(); 
} 
test(); 
?>

-------------------------------------------------------------------------------
输出结果：
Mr. zhan 12 male
Mr. zhan 13 male
Mr. zhan 14 male

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