一.什么是构造方法
构造方法是类的一种特殊的方法,它的主要作用是完成对新对象初始化.
特点:
1. 没有返回值.
2. 在创建一个新的对象时,系统会自动调用该类的构造方法完成对新对角的初始化.
语法:
php5: 修饰符 function __construct()
{
//code
}
php4: 修饰符 function 类名()
{
//code
}
注意:
1. php5里对两者都支持,如果两种构造方法同时存在的话,优先选择第一种.
2. 一个类里面默认有一个不带参数为空的构造方法,一旦自定义了一个构造方法,就会覆盖默认的构造方法.
所以说一个类有且只有一个构造方法.
3.一个类只能有一个构造方法.(不能重载)
4.构造方法默认的访问修饰符为public.
二.this关键字
this代表当前对象.可以理解为:谁调用它,它就代表谁.
注意事项:
this不在类定义的使用,只能在类定义的方法中使用.
三.实例
header("Conter-Type:text/html;charset=utf-8");
class Person
{
public $name; //成员变量
public $age;
// function __construct()
//{
// echo "不带参数的构造方法";
//}
function __construct($name,$age)
{
$this -> name = $name;
$this -> age = $age;
echo "带参数的构造方法"."
";
}
//成员方法
function view()
{
//this的引用.
echo "姓名:".$this ->name.", 年龄:".$this ->age;
}
}
//new一个新的对象
//$p = new Person();
$p2 = new Person("李四",13);
$p2 ->view();
?>
结果如下:
带参数的构造方法
姓名:李四, 年龄:13
四:析构方法:
析构方法是PHP5引入的新概念.主要作用:释放资源(比如:释放数据库链接,图片资源...).
语法:
function __destruct(){}
特点:
1.析构方法没有返回值.
2.主要作用是释放资源.并不是销毁对象本身.
3.在销毁对象前,系统自动调用该类的析构方法.
4.一个类最多只有一个析构方法.
五:例子:
header("Conter-Type:text/html;charset=utf-8");
class Person
{
public $name;
public $age;
//构造方法
function __construct($name,$age)
{
$this ->name = $name;
$this ->age = $age;
}
//析构方法
function __destruct()
{
echo "姓名:".$this->name.", 年龄".$this->age."-->销毁
";
}
}
$p1= new Person("小一",18);
$p2= new Person("小二",17);
?>
结果:
姓名:小二, 年龄17-->销毁
姓名:小一, 年龄18-->销毁
分析结论:
1.析构方法会自动调用.
2.析构方法调用的顺序是先创建的对象后被销毁.
3.当一个对象没有引用,被垃圾回收机制确认为垃圾时,调用析构方法.

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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