What is the x7f-xff in this regular expression?

What does the x7f-xff in this regular expression mean to see a regular expression written in the source code?
/\ <\ {\ S * \ $ [a-zA-Z _ \ x7f-xff] [a-zA-Z0-9 _ \ x7f-\ xff] \ s * \} \>/I

What does \ x7f-xff mean in

Reply to discussion (solution)

\ X7f-\ xff indicates that the ASCII character ranges from 127 to 255, where \ is an escape character.

Why is the value range from 127 to 255? Sorry, let's have a deeper look.

Echo bin2hex ('whe'); // ceaacab2c3b4

Echo "\ xce \ xaa \ xca \ xb2 \ xc3 \ xb4"; // why?

Why is the value range from 127 to 255? Sorry, let's have a deeper look.

It may be an IP address category.
A: The first digit is 0; 1.0.0.0 ~ 126.0.0.0; 24-bit host number
B: The first two digits are 10; 128.1.0.0 ~ 191.255.0.0; host No. 16 bits
C: The first three digits are 110; 192.0.1.0 ~ 223.255.255.0; host No. 8 bits
D: the first four digits are 1110; 224.0.0.0 ~ 239.00000000255
E: the first four digits are 1111; 240.0.0.0 ~ 255.255.255.254

!!! What does this have to do with the IP address !!!

Except when the brackets themselves or connectors represent the range, the brackets are not metacharacters. So [\ x7f-xff] represents the character group of \, x, 7, f-x, f, f.

Sorry, yesterday's reply was incorrect. correct this. The metacharacter "\ xn" is used to match n, where n is the hexadecimal escape value, the value must be determined by two numbers. For example, "\ x41" matches "A", and "\ x411" is equivalent to "A1 ". The connector "-" represents a range in the character group (a string in parentheses) (if not at the beginning ). It is worth noting that the metacharacter rules are different within and outside the character group.