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PHP Filters are used to validating and sanitizing external input data. Validating data (Validate that external data is in the proper format or not) Sanitizing data (Remove illegal characters from external data).
PHP has many functions for checking, validating and cleaning external inputs.
PHP filter_list() functions is used to fetch the list of PHP filter extensions.
Below is the example of PHP filter_list() and filter_id() functions
<!DOCTYPE html>
<html>
<body>
<h1>PHP Filter</h1>
<table>
<tr>
<th>Filter Name</th>
<th>Filter ID</th>
</tr>
<?php
foreach (filter_list() as $filter) {
echo '<tr><td>' . $filter . '</td><td>' . filter_id($filter) . '</td></tr>';
}
?>
</table>
</body>
</html>
The above code produces the following results
Outputs:
Filter Name Filter ID
int 257
boolean 258
float 259
validate_regexp 272
validate_url 273
validate_email 274
validate_ip 275
string 513
stripped 513
encoded 514
special_chars 515
full_special_chars 522
unsafe_raw 516
email 517
url 518
number_int 519
number_float 520
magic_quotes 521
callback 1024
Mostly application receive external data and external data can be in right format or wrong format, so we should validate, verify and cleaning the external data.
These are the PHP filter_var() function with different parameters
filter_var($ip, FILTER_VALIDATE_IP);
filter_var($string, FILTER_SANITIZE_STRING);
filter_var($int, FILTER_VALIDATE_INT);
filter_var($url, FILTER_SANITIZE_URL);
filter_var($email, FILTER_VALIDATE_EMAIL);
filter_var($email, FILTER_SANITIZE_EMAIL);
