PHP regular expression method to verify special characters

With the rapid development of the Internet, more and more websites have emerged. In the process of developing these websites, regular expressions are increasingly used. For example, when users enter usernames, passwords and other sensitive information on the registration page, in order to ensure the security of the entered data, developers usually use regular expressions to ensure the legitimacy of the data. This article will focus on the method of verifying special characters with PHP regular expressions to help developers better protect the security of user data.

1. What is a regular expression?

A regular expression is an expression used to match text strings. It consists of text and special characters and can be used to check whether a string matches a certain pattern. PHP, as a popular server-side language, can provide powerful string processing capabilities using regular expressions. Regular expressions in PHP are usually enclosed between two forward slashes, for example: "/pattern/".

2. Regular expression in PHP to verify special characters code

The following is a piece of code in PHP to verify whether the input string contains special characters:

function check_special_chars($str) {
    if(preg_match('/[^a-zA-Z0-9_]/', $str)) {
        return false;
    }
    return true;
}

In the above code, the preg_match() function is used to check whether the string matches the specified regular expression. The regular expression "/¹/" specifies the set of characters that the function needs to match, where "^" means non, which means it does not match a~z, A~Z, or 0 All characters except ~9 and underscore (_). If the input string contains any of these characters, the function returns false, otherwise it returns true.

3. Regular expression verification function in PHP

In addition to the preg_match() function, PHP also provides some other regular expression verification functions, as shown in the following table:

##preg_match() Perform a regular expression matchpreg_replace()Perform a regular expression search and replacepreg_split( )Split a string into an array by a regular expressionpreg_quote()Escape regular expression characterspreg_grep()Returns the elements in the array that match a regular expressionpreg_last_error()Returns the last The error code returned by a PCRE regular execution

Function	Description

These functions have their own usage methods and parameters. For details, please refer to the official PHP documentation or related books.

Use regular expressions to validate usernames, passwords, and other fields

The following are some examples that demonstrate how to use regular expressions to validate usernames, passwords, and other sensitive fields. information.

Verify username

Verification username usually needs to comply with some rules, such as only containing letters, numbers and underscores, and the length must be between 6-16 characters . The following is a regular expression for verifying usernames:

'/^[a-zA-Z0-9_]{6,16}$/'

This regular expression uses ^ to indicate the first character match, $ to indicate the end of the string, {6,16} to indicate that the character length must be between 6 and 16 .

Verification password

The verification password also needs to comply with some rules, such as containing at least one number, one uppercase letter and one lowercase letter, and the length is 8-20 characters between. The following is a regular expression for verifying passwords:

'/^(?=.*d)(?=.*[a-z])(?=.*[A-Z]).{8,20}$/'

This regular expression uses ^ to indicate the first character match, $ to indicate the end of the string, (?=.

d) to indicate that it contains at least one number, ( ?=.[a-z]) means that it contains at least one lowercase letter, (?=.*[A-Z]) means that it contains at least one uppercase letter, .{8,20} means that the character length must be between 8 and 20.

Verify email address

Verification of email address is also a function that developers often need to implement. The following is a regular expression for verifying email addresses:

'/^[a-zA-Z0-9_-]+@[a-zA-Z0-9_-]+(.[a-zA-Z0-9_-]+)+$/'

This regular expression uses ^ to indicate the first character match, $ to indicate the end of the string, @ to indicate an "@" symbol, [a-zA-Z0- 9_-] means that the email name can contain letters, numbers, underscores and half-width minus signs, (.[a-zA-Z0-9_-]) means that the email domain name can contain multiple sub-domain names separated by half-width dots (.), The last subdomain name must be 2-4 letters or numbers.

Summary

Through the introduction of this article, we have learned about the method of PHP regular expression verification of special characters, and learned some common regular expression verification techniques. As developers, we need to ensure the security of user data. Using regular expressions to verify the validity of input data is a very important step. I hope this article can be helpful to everyone, and let us work together to make the Internet safer.

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