Regular metacharacters and ordinary characters

This time I will bring you regular metacharacters and ordinary characters. What are the precautions when using regular metacharacters and ordinary characters? The following is a practical case. Let’s take a look. take a look.

If you want to learn regular expressions, understanding metacharacters and ordinary characters is a difficulty that must be overcome. No need to remember it deliberately. The editor below brings you knowledge about regular expression metacharacters and ordinary characters, let’s take a look.

According to the regular expression grammar rules, the matching pattern of the regular expression is composed of a series of characters.

1. Ordinary characters:

Most characters can only describe themselves. These characters are called ordinary characters, such as all letters. and numbers.

That is to say, ordinary characters can only match the same characters in string.

2. Metacharacters:

Since ordinary characters can only match the same characters as themselves, the flexibility and power of regular expressions The matching function cannot be fully displayed, so the regular expression specifies a series of special characters . These characters are not matched according to the direct quantity of characters, but have special semantics,

For example, the following characters:

^ $ . * + ? = ! : | \ / ( ) [ ] { }

Although the above characters have special meanings, some characters only have special meanings in certain contexts.

If you want to match these character literals with special meanings, you need to add a backslash (\) in front of these characters to escape. For example, if I want to match a $ literal, I need to write it as \$, otherwise it will match. An ending position. It is precisely because of the existence of these special characters that regular expressions have powerful functions.

Because they are the basic characters for constructing various regular expressions that match complex text, they are called metacharacters.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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