Analysis of escape character encoding and decoding functions in PHP

Escape character is a very important concept in PHP programming. The function of escape characters is to make special characters (such as single quotation marks, double quotation marks, backslashes, etc.) not be interpreted as other meanings in the string, but be used literally. However, in some special cases, we need to decode escaped characters and return their actual special characters, which is the function of PHP decoding of escaped characters.

First, we need to know some common escape characters. For example, single quotes in a single quote string need to be escaped, otherwise it will lead to syntax errors:

$string = 'It's a sunny day! ';

Double quotation marks and backslashes in double quotation mark strings also need to be escaped:

$string = "She said, "I'm sorry."";

Backslash strings are used to represent some special characters, such as tabs, carriage returns, line feeds, etc.

$string = "First lineSecond line Third line Forthline";

In PHP, we can use backslashes to escape. However, in some scenarios of reading data, we need to decode the escaped characters in the string to get the actual special characters. To solve this problem, PHP provides some built-in functions to encode and decode escaped characters.

The first function is addslashes, which is used to escape code the special characters in the string. It will add a backslash before special characters such as single quotation marks, double quotation marks, backslashes, tabs, carriage returns, line feeds, etc., and make them ordinary characters:

$string = "It's a sunny day! "; $encoded_string = addslashes($string); echo $encoded_string; //output It's a sunny day!

Addslashes function also plays an important role in preventing SQL injection attacks.

Next, let's take a look at the inverted semantic character function stripslashes. It is used to decode escaped characters in a string and restore them to actual special characters. We can use this function to decode the return value of the above coding function:

$string = "It's a sunny day! "; $encoded_string = addslashes($string); $decoded_string = stripslashes($encoded_string); echo $decoded_string; //output It's a sunny day!

In addition to the above two functions, we can also use the html_entity_decode function. This function is used to parse HTML entities and convert them into actual characters. For example, < will be decoded as >. It can also be used to decode escape characters:

$string = "She said, "I'm sorry.""; $encoded_string = htmlentities($string); $decoded_string = html_entity_decode($encoded_string); echo $decoded_string; //output She said, "I'm sorry. "

In a word, escape character is a very common programming concept, and the escape character encoding and decoding functions in PHP can help us to deal with special characters in strings more conveniently.