Detailed explanation of two PHP regular expression special characters_PHP tutorial

PHP regular expression special characters "[ ]" and "", so what are they? What is the specific operation? Why are they special characters? Is there anything special about their use? Let's take a look at the specific introduction.

The other two very important special characters are "[ ]". They can match characters that appear in "[]". For example, "/[az]/" can match a single character "a" or "z"; if the above expression is changed to "/[a-z]/" , you can match any single lowercase letter, such as "a", "b", etc.

About the PHP regular expression special character "[ ]":

If "^" appears in "[]", it means that this expression does not match" Characters appearing within []", such as "/[^a-z]/" do not match any lowercase letters! And the regular expression gives several default values ​​of "[]":

◆[:alpha:]: matches any letter

◆[:alnum:]: matches any letter and Digits

◆[:digit:]: Matches any digits

◆[:space:]: Matches spaces

◆[:upper:]: Matches any uppercase letters

◆[:lower:]: matches any lowercase letter

◆[:punct:]: matches any punctuation mark

◆[:xdigit:]: matches any 16 Base numbers

About PHP regular expression special characters "":

The following special characters have the following meanings after being escaped by the escape symbol "":

◆s: Matches a single space character

◆S: Matches all characters except a single space character.

◆d: Used to match numbers from 0 to 9, equivalent to "/[0-9]/".

◆w: Used to match letters, numbers or underscore characters, equivalent to "/[a-zA-Z0-9_]/".

◆W: Used to match all characters that do not match w, equivalent to "/[^a-zA-Z0-9_]/".

◆D: used to match any non-decimal numeric characters.

.◆: Used to match all characters except newline characters. If modified by the modifier "s", "." can represent any character.

That’s it for you about the introduction of special characters in PHP regular expressions. I hope it will be helpful for you to understand and master the use of special characters in PHP regular expressions.

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