PHP Character security filter function use summary, PHP characters function Summary _php tutorial

PHP Character security filter function use Summary, PHP function summary

In the Web development process, we often want to get data from users from all over the world. However, we "can never trust the data entered by those users." So in a variety of web development languages, there are functions that guarantee user input data security. In PHP, there are some useful and handy functions that can help you prevent problems like SQL injection attacks, XSS attacks, and so on.

1. Mysql_real_escape_string ()

This function has been a great help in preventing SQL injection attacks in PHP, with special characters, such as single quotes and double quotes, plus a "backslash" to ensure that the user's input is safe before it is queried. But you should be aware that you are using this function in connection with the database.
But now mysql_real_escape_string () This function is basically no, all new application development should use a library like PDO to operate the database, that is, we can use ready-made statements to prevent SQL injection attacks.

2. Addslashes ()

This function is similar to the above mysql_real_escape_string () and is also a backslash for special characters, but be careful not to use this function when setting the value of MAGIC_QUOTES_GPC in file php.ini to "on". MAGIC_QUOTES_GPC = On, automatically runs Addslashes () for all GET, POST, and COOKIE data. Do not use Addslashes () for strings that have been MAGIC_QUOTES_GPC escaped, because this results in double-layer escaping. You can check the value of this variable by using the GET_MAGIC_QUOTES_GPC () function in PHP.

3. Htmlentities ()

This function is useful for filtering user input data, and it can convert characters to HTML entities. For example, when the user enters the character "<", the function will be converted into an HTML entity "<" (see the source code will see "<"), thus preventing XSS and SQL injection attacks, for unrecognized character sets will be ignored and replaced by iso-8859-1

4. Htmlspecialchars ()

This function is similar to the above, some characters in HTML have a special meaning, if you want to embody this meaning, it will be converted to an HTML entity, this function returns the converted string.

5. Strip_tags ()

This function can remove all html,javascript and PHP tags from the string, but you can also ignore some specific tags by setting the second parameter of the function.

6. Intval ()

Intval actually does not belong to the filter function, its function is to convert the variable into an integer type. Useful when we need to get an integer parameter, you can use this function to make your PHP code more secure, especially if you are parsing integer data such as ID and age.

These are the PHP built-in string filter functions, very simple and practical, I hope that the small partners can use them well.

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