php手册里面有这样的解释 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.
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在处理字符变量的算数运算时,PHP 沿袭了 Perl 的习惯,而非 C 的。例如,在 Perl 中 'Z'+1 将得到 'AA',而在 C 中,'Z'+1 将得到 '['(ord('Z') == 90,ord('[') == 91)。注意字符变量只能递增,不能递减,并且只支持纯字母(a-z 和 A-Z)。
手册中有写!
php手册里面有这样的解释
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.