Detailed explanation of escape and restoration techniques in PHP

Escape and restore in PHP are very important concepts. This is because when developing web applications, users will submit data to the server. The data may contain special characters, and these special characters may be leading to security issues. Therefore, we need to escape and restore these special characters to ensure data security. This article will introduce escaping and restoration techniques in PHP.

1. PHP Escape Technology

The method of escaping in PHP is through a function: addslashes(). The so-called "escaping" means to perform special processing on some special characters so as not to treat them as ordinary characters. These special characters are usually quotation marks, backslashes, etc. When these characters appear in certain commands or statements, they will be used as delimiters of commands or statements, leading to program errors or injection attacks.

addslashes()The function is to add a backslash before special characters to escape them. For example:

$str = "This is John's book";
$str = addslashes($str);

The output result is: "This is John\'s book". As you can see, the single quotes are converted into "\'", which prevents the single quotes from being used as statement or command delimiters. Similarly, the backslash is also escaped into "\", which prevents the backslash from being interpreted as an escape character in regular expressions.

In addition to the addslashes() function, there are some other escape functions, such as htmlentities() and htmlspecialchars(). The function of these two functions is to convert all HTML tags into corresponding entities. This is because in HTML, certain tags have special meaning and may cause problems on the page if not escaped. Therefore, using these functions can ensure that our page displays normally and avoid any problems.

2. PHP restoration technology

After obtaining the data from the user, we need to restore it to the original string. This is the restoration technique. In PHP, there are two functions that restore escaped special characters to original characters: stripslashes() and html_entity_decode(). Among them, the stripslashes() function is to remove the backslash before special characters to restore the string. For example:

$str = "This is John\'s book";
$str = stripslashes($str);

The output result is: "This is John's book". As you can see, the backslash in front of the single quotation mark is removed, and the single quotation mark is restored to the original character.

For HTML entities, we can use the html_entity_decode() function to restore it to the original string. For example:

$str = "This is 40% discount";
$str = htmlentities($str);
$str = html_entity_decode($str);

The output result is: "This is 40% discount". As you can see, the original string contains a "%" symbol, and after using the htmlentities() function, the percent sign is converted into an HTML entity "%". After using the html_entity_decode() function, % is restored to the original character "%".

3. Conclusion

The escaping and restoration technologies in PHP are very important. They can help us protect the security of web applications and avoid unnecessary problems. When writing code, we should learn to use these technologies correctly, and when processing user-submitted data, we must escape it to avoid attacks such as SQL injection.

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