What are the differences between (parentheses), [braces] and {curly braces} in regular expressions

This article mainly introduces the regular expressions (parentheses), [braces], {curly braces} what are the differences, have a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, let the editor take you to understand it.

The () [] {} of a regular expression has different meanings.

() is to extract the matching string. If there are several () in the expression, there are several matching strings.

(\ s*) A string that represents consecutive spaces.

[] is the range of characters that define a match. For example, [a-zA-Z0-9] means that the characters in the corresponding position should match English characters and numbers. [\ s*] indicates a space or a * sign.

{} is generally used to indicate the length of a match, for example,\ s {3} means to match three spaces, and\ s [1pr 3] means to match one to three spaces.

(0-9) match'0-9 'itself. [0-9] * matching numbers (note that there is a *, which can be empty) [0-9] + matching numbers (note that there is a + after it, which cannot be empty) {1-9} spelling error.

[0-9] {0jue 9} represents a numeric string of length from 0 to 9.

For example: filter content in PHP with numbers or spaces in it

Preg_replace ("/\ d {1,}\ s {0jue 1} /", "xxxxxxxx", $signaturecontent); Thank you for reading this article carefully. I hope the article "what are the differences between regular expressions (parentheses), [braces] and {curly braces}" shared by the editor will be helpful to you. At the same time, I hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!