PHP escape characters and their applications

In PHP, sometimes you need to insert some special characters into the string, such as quotation marks, newline characters, etc., but these special characters will affect the splitting and processing of the string. In order to prevent this situation, you can use escape characters to escape these special characters into ordinary characters to avoid abnormal situations.

In PHP, common escape characters include the following:

1. Escape characters available in double quote strings:

Escape Meaning character Description
\n Line feed character
\r Carriage return character
\t Tab character
\ Backslash
$ Dollar sign
\" Double quotation mark

2. Escape characters available in single quote strings:

Escape character Description
\ Backslash
\' Single quote

In addition to the common escape characters mentioned above, PHP also supports the use of \x and \u escape sequences to represent any characters, such as:

Escape sequence Description
\xYY YY is two 16-bit characters System digits, representing characters with ASCII code YY
\uYYYY YYYY are four hexadecimal digits, representing characters with Unicode code YYYY

Escape characters are widely used, especially in operating databases When doing this, it is often necessary to escape some special characters to avoid security issues such as SQL injection. Common methods of using escape characters are as follows:

1. addslashes() function

The addslashes() function can be used to add backslashes before certain characters in a string, such as single quotes, double quotes, etc. The usage method is as follows:

$string = "It's a beautiful day.";
echo addslashes($string);

The output result is:

It\'s a beautiful day.

2. stripslashes() function

The stripslashes() function can be used to remove all backslashes added by the addslashes() function in the string and restore the special characters in the string. The usage method is as follows:

$string = "It\ 's a beautiful day.";
echo stripslashes($string);

The output result is:

It's a beautiful day.

3. mysqli_real_escape_string() Function

mysqli_real_escape_string() function can be used to escape certain characters to avoid security issues such as SQL injection. The usage method is as follows:

$string = "It's a beautiful day. ";
$escaped_string = mysqli_real_escape_string($mysqli, $string);
echo $escaped_string;

where $mysqli is the connection handle returned by the mysqli_connect() function. The output result is:

It\'s a beautiful day.

In addition to the above three common escape character usage methods, there are many other escape characters in PHP, and the usage methods are also not exactly. In actual development, different escape characters and their usage methods should be selected according to specific situations to ensure the robustness and security of the code.

Summary

Escape characters are widely used in PHP and can be used to escape special characters into ordinary characters to avoid string processing exceptions. Common escape characters include single quotes, double quotes, backslashes, etc. For different characters, different escape methods should be selected according to the specific situation. The correct use of escape characters can help improve the robustness and security of the code, and is worthy of in-depth study and mastery by developers.

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