$a=new A 和 $a= & new A 到底有没有区别?
$a=new A; // $a 是 new A 的 指针 的一个拷贝 ( $a 保存的是 指针本身)
$a=& new A; // $a 是 new A 的 指针 的一个 引用 ( $a 保存的是 指针的地址)
以上说法正确吗?
另外:
$c= & $a 的时候, 为什么会把 $a 也变成了 A 的指针的 引用 ?
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$c= & $a 的时候, 为什么会把 $a 也变成了 A 的指针的 引用 ?
是沿袭于 $a=& new A; ?
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嘻嘻,&在C里面是取址符
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php里的变量都是指针,但对于string,int等,赋值=是对象的拷贝,对于对象,赋值=是地址的拷贝(也就是引用),我现在感觉这么理解挺好的。
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无论是 php 的什么版本 new 算符产生的都是引用
$a =& new A;
这种写法是不准确的。把一个对象的引用的引用赋给变量?
所以在 php5.3 就新增了一个错误类型,来规范书写的格式
Deprecated: Assigning the return value of new by reference is deprecated
php5.2及以前不报错,但并不等于就不是错。
就如同你屏蔽了 E_NOTICE 级别错误,但不能说就没有错,毕竟还是使用了 未经定义的变量或下标了嘛
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很纠结的问题
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正统的用法
$c = new A;
就当其它的用法都是扯淡了。
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唉,还是看牛人的博客吧
http://www.laruence.com/2008/09/19/520.html
解释了你6楼的问题
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查了一下手册:
关于引用:
在 PHP 中引用意味着用不同的名字访问同一个变量内容。这并不像 C 的指针,替代的是,引用是符号表别名。注意在 PHP 中,变量名和变量内容是不一样的,因此同样的内容可以有不同的名字。最接近的比喻是 Unix 的文件名和文件本身――变量名是目录条目,而变量内容则是文件本身。引用可以被看作是 Unix 文件系统中的 hardlink。
关于new:
Construct an instance of "type" and store the reference to the object into "result".
所以$c = new A;是赋值引用而不是做对象拷贝。 $c = &new A; 是错误的写法。
自 PHP 5 起,new 自动返回引用,因此在此使用 =& 已经过时了并且会产生 E_STRICT 级别的消息。
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关于赋值:
注意赋值运算将原变量的值拷贝到新变量中(传值赋值),所以改变其中一个并不影响另一个。这也适合于在很密集的循环中拷贝一些值例如大数组。也可以使用引用赋值,用 $var = &$othervar; 语法。引用赋值意味着两个变量都指向同一个数据,没有任何数据的拷贝。有关引用的更多信息见引用的说明。在 PHP 5中,对象总是通过引用赋值的,除非明确使用新的 clone关键字。
- PHP code
<?php $a = 1; $b = &$a; $c = $a; $b = 2; echo "a:$a, b:$b, c:$c\n"; $d = $b; $d = 3; echo "a:$a, b:$b, c:$c\n"; class A { public $foo = 1; } $oa = new A; $ob = $oa; $oa->foo = 2; echo "oa:$oa->foo, ob:$ob->foo\n"; ?> <br><font color="#e78608">------解决方案--------------------</font><br>$a =1;<br>$b = & $a; <br>不同的变量指向同一个地址,当其中一个($b=2)改变,那么另一个也会改变($a=2).但是把$b 销毁掉(unset($b))后 $a = 2还是存在的。<br><br>$a =1;<br>$b = $a;//他就是$b=1<br>=> $a =1;$b=1;<br>$b $a 没有一毛钱的关系 ,你是你我是我,谁也管不着谁。<br><br>$a=& new A; 这种东西我还真不用的,没啥意思。 <div class="clear"> </div>

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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