因为php是一个脚本语言,因此它的过度的灵活性,会导致它在解析的时候会产生歧义,一般来说我们是要避免这些歧义的,这里来小小的举一个例子吧,朋友们不妨看看下面的代码会输出什么:
<?php $var = 'hello';$var_ = 'world';echo "$var_$var_";echo "<br />";echo "{$var}_$var_";
对于上面的代码,第一个echo永远会输出"worldworld",因为它在解析的时候不会单独的解析$var,而是解析成为$var_,而后面的则会解析成为hello_world,也就是说我们用花括号强制改变了它的优先级。
其实还有一个很经典的例子,就是在数组上,直接贴代码:
// DaiJie 的代码中有一种以上的解释,php解释器不知道什么是对的。$c = array('d'=>'e');echo "{$c}['d']"; // Array['d']$c = array('d'=>'e');echo "${c['d']}"; // e
上面我们使用大括号来强制性的改变它的优先级,对于具体例子就不多解释了。顺便说一下,本文主要参考sf,贴一下传送门:http://segmentfault.com/q/1010000000120010
版权声明:本文为博主原创文章,未经博主允许不得转载。

The article explains how to create, implement, and use interfaces in PHP, focusing on their benefits for code organization and maintainability.

The article discusses the differences between crypt() and password_hash() in PHP for password hashing, focusing on their implementation, security, and suitability for modern web applications.

Article discusses preventing Cross-Site Scripting (XSS) in PHP through input validation, output encoding, and using tools like OWASP ESAPI and HTML Purifier.

Autoloading in PHP automatically loads class files when needed, improving performance by reducing memory use and enhancing code organization. Best practices include using PSR-4 and organizing code effectively.

PHP streams unify handling of resources like files, network sockets, and compression formats via a consistent API, abstracting complexity and enhancing code flexibility and efficiency.

The article discusses managing file upload sizes in PHP, focusing on the default limit of 2MB and how to increase it by modifying php.ini settings.

The article discusses nullable types in PHP, introduced in PHP 7.1, allowing variables or parameters to be either a specified type or null. It highlights benefits like improved readability, type safety, and explicit intent, and explains how to declar

The article discusses the differences between unset() and unlink() functions in programming, focusing on their purposes and use cases. Unset() removes variables from memory, while unlink() deletes files from the filesystem. Both are crucial for effec


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

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 Linux new version
SublimeText3 Linux latest version

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Dreamweaver CS6
Visual web development tools

Dreamweaver Mac version
Visual web development tools

WebStorm Mac version
Useful JavaScript development tools
