字符串的递增行为-PHP复活节彩蛋? [英] Increment behavior on strings - PHP easter egg?

问题描述

$var = 'test_1';
var_dump(++$var); // string(6) "test_2" 

$var2 = '1_test';
var_dump(++$var2); // string(6) "1_tesu"

$var3 = 'test_z';
var_dump(++$var3); // string(6) "test_a"

$var4 = 'test_';
var_dump(++$var4); // string(5) "test_"

因此，很显然，如果最后一个字符是数字，则对字符串使用增量运算符的作用是增加数字，增加字母，然后如果最后一个字符位于字母中并且没有任何字符，则重置为一次z对非字母数字字符有效.

So apparently, using an increment operator on a string has the effect of increasing the digit if the last character is a number, increasing the letter and then resetting to a once z if the last character is in the alphabet, and has no effect on non alpha numeric characters.

这是许多脚本语言所期望的标准功能吗?还是我刚刚找到了PHP复活节彩蛋?

Is this a standard feature, expected in many scripting languages, or did I just find a PHP easter egg?

推荐答案

PHP在处理算术运算时遵循Perl的约定 在字符变量上，而不是在C上.例如，在PHP和Perl中，$ a = 'Z'; $ a ++;将$ a转换为"AA"，而在C中将a转换为"Z"； a ++;变成 '['('Z'的ASCII值为90，'['的ASCII值为91).注意 字符变量可以递增但不能递减，即使如此 仅支持纯ASCII字符(a-z和A-Z). 递增/递减其他字符变量无效， 原始字符串不变.

PHP follows Perl's convention when dealing with arithmetic operations on character variables and not C's. For example, in PHP and Perl $a = 'Z'; $a++; turns $a into 'AA', while in C a = 'Z'; a++; turns a into '[' (ASCII value of 'Z' is 90, ASCII value of '[' is 91). Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported. Incrementing/decrementing other character variables has no effect, the original string is unchanged.

-> http://php.net/manual/en/language.operators.increment.php

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