Question

PHP构造函数的一个问题

比如这一段代码
class Person{
var $name;
var $sex;
var $age;

function __construct($name,$sex,$age){
$this->name = $name;
$this->sex = $sex;
$this->age = $age;

function say(){
echo "我的名字：".$this->name."，性别：".$this->sex."，年龄：".$this->age."<br />";
}

这是一个很普通的一个类，三个变量，，一个构造函数，一个打印的函数

PHP只能有一个构造方法。我度着创了四个对象
$person1 = new Person("张三","男",20);
$person2 = new Person("张三","男");
$person3 = new Person("张三");
$person4 = new Person();

无参， 1参，2参。3参
最后都都调用say()我的结果是。都能顺便的打印出来。但是前面有一大串的警告错误代码。，感觉就是创建0 1 2 个参数的时候出现的。请问这是正常的呢。还是怎么顺事。怎么避免。

Warning: Missing argument 3 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 26 and defined in C:\xampp\htdocs\test\test.php on line 9

Notice: Undefined variable: age in C:\xampp\htdocs\test\test.php on line 12

Warning: Missing argument 2 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 27 and defined in C:\xampp\htdocs\test\test.php on line 9

Warning: Missing argument 3 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 27 and defined in C:\xampp\htdocs\test\test.php on line 9

Notice: Undefined variable: sex in C:\xampp\htdocs\test\test.php on line 11

Notice: Undefined variable: age in C:\xampp\htdocs\test\test.php on line 12

Warning: Missing argument 1 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 28 and defined in C:\xampp\htdocs\test\test.php on line 9

Warning: Missing argument 2 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 28 and defined in C:\xampp\htdocs\test\test.php on line 9

Warning: Missing argument 3 for Person::__construct(), called in C:\xampp\htdocs\test\test.php on line 28 and defined in C:\xampp\htdocs\test\test.php on line 9

Notice: Undefined variable: name in C:\xampp\htdocs\test\test.php on line 10

Notice: Undefined variable: sex in C:\xampp\htdocs\test\test.php on line 11

Notice: Undefined variable: age in C:\xampp\htdocs\test\test.php on line 12

Answer 1

这个肯定是要报错的，
构造函数中有三个参数，而且参数都没有默认值，也就是说，你在初始化一个对象的时候一定要把这三个参数填写完整才可以。
这个是正常的，避免不了，如果要避免的话就是把那三个参数填写完整。

追问

确实我后来试着把name sex这两个设轩""但是age再怎么也要个0就可以了。。是否只能这样做啊。。

追答

是的，只能是加上默认值。

Answer 2

你的构造函数要调用三个参数呀,你给的参数不够,当然出错.
你可以把构造函数这样写
function __construct($name="张三",$sex="男",$age=20){
$this->name = $name;
$this->sex = $sex;
$this->age = $age;
}
即设置一个默认值即可