Usage of shortest matching pattern in regular expressions

If there is a text, you only want to match the shortest possible one, not the longest one. This article mainly introduces you to the relevant information about the usage of the shortest matching pattern in regular expressions.

Preface

Recently, I wanted to use regular expressions to grab something from a web page. The content was not complicated, but many problems arose. . Not much to say below, let’s take a look at the detailed introduction:

When we use regular expressions to match the beginning and end of a tag, such as matching 4a249f0d628e2318394fd9b75b4636b1hello world473f0a7621bec819994bb5020d29372a The opening and closing tags of h1 in

maybe many people will write like this

/<.*h1>/g

But like this Is it really possible?

Because the * matching character matches zero or more of the previous character, and it is a greedy matching

, so what you get will be the following result.

Obviously this is not what we want, so how to change greedy matching into minimum matching,

/<.*?h1>/g

The above writing method is enough, as shown below:

In fact, the principle should be very simple, because? Also Greedy matching, and can only match 0 to 1,

, so it will end when it matches the first one, thus preventing * from matching multiple greedy ones.

The above content is the usage of the shortest matching pattern in regular expressions. I hope it can help everyone.

Related recommendations:

PHP regular expression collection

Detailed explanation of commonly used functions in php regular expressions

Summary of regular expressions commonly used in php forms

The above is the detailed content of Usage of shortest matching pattern in regular expressions. For more information, please follow other related articles on the PHP Chinese website!