Explain in detail the implementation principle of PHP's verification function

4. Writing PHP programs

In PHP verification websites, PHP programs are the top priority. The program is responsible for connecting to the database, validating user input, processing data and other operations. PHP programs can use if-else statements, switch statements and other conditional judgment statements to implement different functions. For example, whether the input is empty, whether the format is correct, etc. Entering correct data can be stored by the program, entering incorrect data will return an error message to the user.

5. Form submission

When the form is submitted, the data in the form needs to be sent to the PHP program for processing in the form of a POST or GET request. The data submitted by the form will be verified and checked by the PHP program, and the processing results will be returned after the processing is completed. There are many techniques for collecting and validating form data in PHP programs, such as $_POST, $_GET, $_SESSION, $_COOKIE, etc.

3. PHP verification implementation principle

In the above steps, by understanding the implementation principle of PHP verification, you can better build a PHP verification website.

1. Filtering user input

In PHP verification, filtering user input is the basic verification principle. This can be achieved using PHP's built-in filter_var() function. This function can be used to verify input strings, numbers, emails, URLs and other information to prevent users from entering illegal characters into the database.

2. Regular expression verification

Regular expression is a powerful verification method. Regular expressions can be used to accurately match input strings in PHP programs for verification purposes. For example, regular expressions can be used to verify that the entered email address and mobile phone number are correct.

3. Prevent SQL injection attacks

When using PHP to verify a website, you need to pay attention to SQL injection attacks to avoid allowing attackers to insert SQL statements into the input information to attack the database. For this case, you can use the mysqli_real_escape_string() function to filter the SQL statements in the input.

4. Input length limit

In order to ensure the security of the website, it is necessary to limit the length of user input to prevent users from entering too long strings or causing other unnecessary The problem. You can use the strlen() function to limit the length of the input, or use other functions to limit it. You can also add the maxlength attribute to the HTML form to limit the input length.

4. Summary

PHP verification is an important link that cannot be ignored when building a website. PHP validation can improve website security and user experience. When building a PHP verification website, you need to clarify the specific needs and operations of the website, understand technologies such as connecting to the database, designing forms, writing PHP programs and form submission, and master filtering user input, regular expression verification, preventing SQL injection attacks and input length Restrictions and other verification methods. Only through continuous practice can we better master and apply PHP verification technology to make the website more secure, efficient and convenient.

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