The content introduced in this article is about [php classes and objects] objects and references, which has a certain reference value. Now I share it with everyone. Friends in need can refer to
Objects and References
PHP references are aliases, that is, two different variable names point to the same content.
In PHP 5, an object variable no longer holds the value of the entire object. Just save an identifier to access the real object content. When an object is passed as a parameter, returned as a result, or assigned to another variable, the other variable has no reference relationship with the original one, but they both store a copy of the same identifier, which points to the real content of the same object. .
Example #1 引用和对象<?phpclass A {
public $foo = 1;
}
$a = new A;$b = $a; // $a ,$b都是同一个标识符的拷贝
// ($a) = ($b) = <id>$b->foo = 2;echo $a->foo."\n";$c = new A;$d = &$c; // $c ,$d是引用
// ($c,$d) = <id>$d->foo = 2;echo $c->foo."\n";$e = new A;function foo($obj) {
// ($obj) = ($e) = <id>
$obj->foo = 2;
}
foo($e);echo $e->foo."\n";?>User Contributed Notes
/*
Notes on reference:
A reference is not a pointer. However, an object handle IS a pointer. Example:
*/<?phpclass Foo {
private static $used; private $id; public function __construct() {
$id = $used++;
} public function __clone() {
$id = $used++;
}
}$a = new Foo;
// $a is a pointer pointing to Foo object 0$b = $a;
// $b is a pointer pointing to Foo object 0, however, $b is a copy of $a$c = &$a;
// $c and $a are now references of a pointer pointing to Foo object 0$a = new Foo;
// $a and $c are now references of a pointer pointing to Foo object 1, $b is still a pointer pointing to Foo object 0unset($a);
// A reference with reference count 1 is automatically converted back to a value. Now $c is a pointer to Foo object 1$a = &$b;
// $a and $b are now references of a pointer pointing to Foo object 0$a = NULL;
// $a and $b now become a reference to NULL. Foo object 0 can be garbage collected nowunset($b);
// $b no longer exists and $a is now NULL$a = clone $c;
// $a is now a pointer to Foo object 2, $c remains a pointer to Foo object 1unset($c);
// Foo object 1 can be garbage collected now.$c = $a;
// $c and $a are pointers pointing to Foo object 2unset($a);
// Foo object 2 is still pointed by $c$a = &$c;
// Foo object 2 has 1 pointers pointing to it only, that pointer has 2 references: $a and $c;const ABC = TRUE;
if(ABC) {
$a = NULL;
// Foo object 2 can be garbage collected now because $a and $c are now a reference to the same NULL value
} else {
unset($a);
// Foo object 2 is still pointed to $c
}<?php
//The two are meant to be the same$a = "Clark Kent";
//a==Clark Kent$b = &$a;
//The two will now share the same fate.$b="Superman";
// $a=="Superman" too.echo $a;
echo $a="Clark Kent";
// $b=="Clark Kent" too.unset($b);
// $b porced from $a$b="Bizarro";
echo $a;
// $a=="Clark Kent" still, since $b is a free agent pointer now.
//The two are NOT meant to be the same.$c="King";
$d="Pretender to the Throne";echo $c."\n";
// $c=="King"echo $d."\n";
// $d=="Pretender to the Throne"swapByValue($c, $d);
echo $c."\n";
// $c=="King"echo $d."\n";
// $d=="Pretender to the Throne"swapByRef($c, $d);
echo $c."\n";
// $c=="Pretender to the Throne"echo $d."\n";
// $d=="King"function swapByValue($x, $y)
{
$temp=$x;$x=$y;$y=$temp;
//All this beautiful work will disappear
//because it was done on COPIES of pointers.
//The originals pointers still point as they did.}function swapByRef(&$x, &$y)
{
$temp=$x;$x=$y;
$y=$temp;
//Note the parameter list: now we switched 'em REAL good.
}
?>Related recommendations:
[php classes and objects]trait
[php classes and objects]Final keyword
[php classes and objects]late static binding
The above is the detailed content of [php classes and objects] objects and references. For more information, please follow other related articles on the PHP Chinese website!
PHP: An Introduction to the Server-Side Scripting LanguageApr 16, 2025 am 12:18 AMPHP is a server-side scripting language used for dynamic web development and server-side applications. 1.PHP is an interpreted language that does not require compilation and is suitable for rapid development. 2. PHP code is embedded in HTML, making it easy to develop web pages. 3. PHP processes server-side logic, generates HTML output, and supports user interaction and data processing. 4. PHP can interact with the database, process form submission, and execute server-side tasks.
PHP and the Web: Exploring its Long-Term ImpactApr 16, 2025 am 12:17 AMPHP has shaped the network over the past few decades and will continue to play an important role in web development. 1) PHP originated in 1994 and has become the first choice for developers due to its ease of use and seamless integration with MySQL. 2) Its core functions include generating dynamic content and integrating with the database, allowing the website to be updated in real time and displayed in personalized manner. 3) The wide application and ecosystem of PHP have driven its long-term impact, but it also faces version updates and security challenges. 4) Performance improvements in recent years, such as the release of PHP7, enable it to compete with modern languages. 5) In the future, PHP needs to deal with new challenges such as containerization and microservices, but its flexibility and active community make it adaptable.
Why Use PHP? Advantages and Benefits ExplainedApr 16, 2025 am 12:16 AMThe core benefits of PHP include ease of learning, strong web development support, rich libraries and frameworks, high performance and scalability, cross-platform compatibility, and cost-effectiveness. 1) Easy to learn and use, suitable for beginners; 2) Good integration with web servers and supports multiple databases; 3) Have powerful frameworks such as Laravel; 4) High performance can be achieved through optimization; 5) Support multiple operating systems; 6) Open source to reduce development costs.
Debunking the Myths: Is PHP Really a Dead Language?Apr 16, 2025 am 12:15 AMPHP is not dead. 1) The PHP community actively solves performance and security issues, and PHP7.x improves performance. 2) PHP is suitable for modern web development and is widely used in large websites. 3) PHP is easy to learn and the server performs well, but the type system is not as strict as static languages. 4) PHP is still important in the fields of content management and e-commerce, and the ecosystem continues to evolve. 5) Optimize performance through OPcache and APC, and use OOP and design patterns to improve code quality.
The PHP vs. Python Debate: Which is Better?Apr 16, 2025 am 12:03 AMPHP and Python have their own advantages and disadvantages, and the choice depends on the project requirements. 1) PHP is suitable for web development, easy to learn, rich community resources, but the syntax is not modern enough, and performance and security need to be paid attention to. 2) Python is suitable for data science and machine learning, with concise syntax and easy to learn, but there are bottlenecks in execution speed and memory management.
PHP's Purpose: Building Dynamic WebsitesApr 15, 2025 am 12:18 AMPHP is used to build dynamic websites, and its core functions include: 1. Generate dynamic content and generate web pages in real time by connecting with the database; 2. Process user interaction and form submissions, verify inputs and respond to operations; 3. Manage sessions and user authentication to provide a personalized experience; 4. Optimize performance and follow best practices to improve website efficiency and security.
PHP: Handling Databases and Server-Side LogicApr 15, 2025 am 12:15 AMPHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.
How do you prevent SQL Injection in PHP? (Prepared statements, PDO)Apr 15, 2025 am 12:15 AMUsing preprocessing statements and PDO in PHP can effectively prevent SQL injection attacks. 1) Use PDO to connect to the database and set the error mode. 2) Create preprocessing statements through the prepare method and pass data using placeholders and execute methods. 3) Process query results and ensure the security and performance of the code.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
Dreamweaver CS6
Visual web development tools
Zend Studio 13.0.1
Powerful PHP integrated development environment
EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
