php 运算符当作变量要怎么做

V2EX = way to explore

V2EX 是一个关于分享和探索的地方

现在注册

已注册用户请登录

这是一个创建于 3300 天前的主题，其中的信息可能已经有所发展或是发生改变。

PHP

变量

运算

当作

4 条回复 • 2015-11-09 14:58:32 +08:00

adexbn

2015-11-09 11:37:01 +08:00

Basics ¶

Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.

Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'

Note: For our purposes here, a letter is a-z, A-Z, and the bytes from 127 through 255 (0x7f-0xff).
Note: $this is a special variable that can't be assigned.

mrgeneral

2015-11-09 14:42:39 +08:00

你是要实现这样？
```php
$a = 1;
$b = 1;
$c = '-';
echo $a.$c.$b;//1-1
echo eval("return {$a}{$c}{$b};");//0
```
但是 eval 函数在很多情况下会被禁用

widdy

2015-11-09 14:58:17 +08:00

switch 吧

Automan

2015-11-09 14:58:32 +08:00

自己动手撸个 parser