什么是PHP中的x7f？

Question

What is x7f and xff in php?

Is it hexa or octal values?

EDIT:

It is given in PHP 5.3 manual that, as a regular expression, class name would be expressed as: [a-zA-Z_\\x7f-\\xff][a-zA-Z0-9_\\x7f-\\xff]* .

can any one help what is the meaning of \\x7f-\\xff in above regular expression?

Answer 1

As per the integer page on PHP.net , the format of hex in PHP is:

hexadecimal : 0[xX][0-9a-fA-F]+

thus it's hex.

Answer 2

As other stated its x7f & xff are hexadecimal code which corresponds to extended ASCII characters that can be added as part of class name in php. ASCII Codes

Answer 3

0x前缀（不仅仅是x ）表示十六进制，因此0x7f为127，0xff为255。