FILTER_SANITIZE_ENCODED constant in PHP

The FILTER_SANITIZE_ENCODED constant in PHP is used with the filter_var() function to URL-encode special characters in a string. This is particularly useful for sanitizing URLs and ensuring they contain only valid characters.

Syntax

filter_var($value, FILTER_SANITIZE_ENCODED, $flags)

Flags and Options

• FILTER_FLAG_STRIP_LOW − Remove characters with ASCII value less than 32

• FILTER_FLAG_STRIP_HIGH − Remove characters with ASCII value greater than 127

• FILTER_FLAG_ENCODE_LOW − Encode characters with ASCII value less than 32

• FILTER_FLAG_ENCODE_HIGH − Encode characters with ASCII value greater than 127

Return Value

The filter_var() function with FILTER_SANITIZE_ENCODED returns the sanitized string with special characters URL-encoded, or FALSE on failure.

Basic Example

Here's a simple example showing how FILTER_SANITIZE_ENCODED URL-encodes special characters −

<?php
    $string = "Hello World! @#$%";
    $encoded = filter_var($string, FILTER_SANITIZE_ENCODED);
    echo $encoded;
?>

Hello%20World%21%20%40%23%24%25

Using FILTER_FLAG_STRIP_HIGH

The following example uses FILTER_FLAG_STRIP_HIGH flag to remove characters with ASCII value greater than 127 −

<?php
    $url = "wwwÅ.exampleÅ.com";
    $sanitized = filter_var($url, FILTER_SANITIZE_ENCODED, FILTER_FLAG_STRIP_HIGH);
    echo $sanitized;
?>

www.example.com

Another Example with Special Characters

Let's see another example with different special characters −

<?php
    $url = "example.com££";
    $sanitized = filter_var($url, FILTER_SANITIZE_ENCODED, FILTER_FLAG_STRIP_HIGH);
    echo $sanitized;
?>

example.com

Using Multiple Flags

You can combine multiple flags using the bitwise OR operator −

<?php
    $string = "Test\x01StringÅ";
    $result = filter_var($string, FILTER_SANITIZE_ENCODED, 
              FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH);
    echo $result;
?>

TestString

Conclusion

The FILTER_SANITIZE_ENCODED constant is essential for URL sanitization, encoding special characters and optionally removing unwanted ASCII characters. Use appropriate flags based on your specific requirements for character handling.