PHP regular expression in action: matching numbers

PHP Regular Expression in Practice: Matching Numbers

Regular expression is a markup language used to describe text patterns. In PHP programming, regular expressions are a powerful tool that allow us to implement powerful string processing functions with very little code. Among them, matching numbers is an important application scenario in regular expressions.

In this article, we will introduce how to match numbers with regular expressions in PHP. We will start with the basics and go deeper step by step to help you understand the principles and practices of PHP regular expression matching numbers.

1. Basic knowledge

In regular expressions, patterns for matching numbers include the following types:

1. d: Matches any number, equivalent to [0 -9]
2. D: Matches any non-numeric characters, equivalent to¹
3. [0-9]: Matches any digits
4. ¹: Match any non-numeric characters

The above patterns are used to match a single number or non-numeric character. To match consecutive numeric or non-numeric characters, you need to use specific quantifiers.

2. Quantifier symbols

Quantifier symbols are used to specify the number of matches for a matching pattern. The following are some commonly used quantifier symbols:

1. : Match one or more character that appears at least once.
2. *: Matches zero or more characters, which may not appear or appear one or more times.
3. ?: Matches zero or one character, which may not appear or appear only once.
4. {n}: Match n characters.
5. {m,n}: Match m to n characters.
6. {m,}: Match at least m characters.

3. Practical drill

The following are some common practical application scenarios and corresponding regular expressions:

1. Match integers or decimals: / ^[ -]?d (.d )?$/

This regular expression can match integers or decimals with positive and negative signs, such as: 1, -5.2, 3.14159, etc., but not Matches character numbers or other types of strings.

2. Matching IP address: /^d{1,3}.d{1,3}.d{1,3}.d{1,3}$/

This regular expression can match legal IP addresses, such as: 192.168.0.1, 10.0.0.1, etc., but does not match illegal IP addresses or other types of strings.

3. Matching mobile phone numbers: /^1[3456789]d{9}$/

This regular expression can match legal mainland Chinese mobile phone numbers, for example: 13888888888 , 13999999999, etc., but does not match illegal mobile phone numbers or other types of strings.

4. Matching password: /^[a-zA-Z0-9]{6,20}$/

This regular expression can match 6 to 20 letters or a password composed of numbers, but does not match illegal passwords or other types of strings.

4. Summary

The above is the basic knowledge and practical exercises on matching numbers with PHP regular expressions. Through learning, we can understand the basic concepts and grammatical rules of regular expressions, and how to apply regular expressions to match numbers. In actual programming, we can combine specific needs and flexibly use regular expressions to improve the efficiency and readability of the code.

1. 0-9↩

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