filter_list & filter_id in PHP to get available filters for data validation

We can display list of available filters by using filter_list function. This function returns an array with list of available filters as elements. Here is the example.

print_r(filter_list());

The output is here

Array ( [0] => int [1] => boolean [2] => float [3] => validate_regexp
 [4] => validate_url  [5] => validate_email [6] => validate_ip [7] => string
 [8] => stripped [9] => encoded [10] => special_chars 
[11] => full_special_chars [12] => unsafe_raw [13] => email
 [14] => url [15] => number_int
 [16] => number_float [17] => magic_quotes [18] => callback )

Now we will modify it by displaying in a formatted output. We used standard array display techniques to display the elements of the array
Here is the code to display output

$ar=filter_list();
	foreach ($ar as $key => $val) {
echo "$key => $val 
";

The output is here ( Note that the serial number is the key number of the array filter_list not the filter ID number )

0 => int 
1 => boolean 
2 => float 
3 => validate_regexp 
4 => validate_domain 
5 => validate_url 
6 => validate_email 
7 => validate_ip 
8 => validate_mac 
9 => string 
10 => stripped 
11 => encoded 
12 => special_chars 
13 => full_special_chars 
14 => unsafe_raw 
15 => email 
16 => url 
17 => number_int 
18 => number_float 
19 => magic_quotes 
20 => add_slashes 
21 => callback

filter_id

WE can get the filter id of the particular filter in PHP by using filter_id function. We will input the name of the filter and get the associated id of it. The list containing name of filter is available at filter_list page. Here is the syntax.

Int filter_id(filter name)

Here is one example echo filter_id('validate_url'); The output of above line is here

We can also display the associated id of all the filters in a single list. Here is the sample code.

$ar=filter_list();

while (list ($key, $val) = each ($ar)) {
echo "$key -> $val : ( ".filter_id($val). " ) <br>";
}

The output is here

0 -> int : ( 257 ) 
1 -> boolean : ( 258 ) 
2 -> float : ( 259 ) 
3 -> validate_regexp : ( 272 ) 
4 -> validate_domain : ( 277 ) 
5 -> validate_url : ( 273 ) 
6 -> validate_email : ( 274 ) 
7 -> validate_ip : ( 275 ) 
8 -> validate_mac : ( 276 ) 
9 -> string : ( 513 ) 
10 -> stripped : ( 513 ) 
11 -> encoded : ( 514 ) 
12 -> special_chars : ( 515 ) 
13 -> full_special_chars : ( 522 ) 
14 -> unsafe_raw : ( 516 ) 
15 -> email : ( 517 ) 
16 -> url : ( 518 ) 
17 -> number_int : ( 519 ) 
18 -> number_float : ( 520 ) 
19 -> magic_quotes : ( 521 ) 
20 -> add_slashes : ( 523 ) 
21 -> callback : ( 1024 )

PHP Filters filter_list:PHP list of filters available and how to display filter_has_var: checking the existence of variable in PHP filter_var: Validating variable using filter id FILTER_VALIDATE_FLOAT: Validating Float data FILTER_VALIDATE_INT: Validating Integer with Maximum and Minimum range FILTER_VALIDATE_REGEXP: Validating Regular Expression FILTER_VALIDATE_EMAIL: Validating Email FILTER_VALIDATE_URL: Validating URL with query string and path FILTER_VALIDATE_IP: Validating IPV4 and IPV6 address FILTER_VALIDATE_BOOLEAN: Validating Boolean variable FILTER_SANITIZE_STRING: Sanitize string FILTER_SANITIZE_URL: Sanitize URL

Questions

What is the purpose of the filter_list() function in PHP?
How does filter_list() retrieve a list of available PHP filters?
What types of filters can be returned by the filter_list() function?
Can you customize or extend the list of filters returned by filter_list()?
How can you use filter_list() to retrieve a specific type of filter, such as validation or sanitization filters?
Does the order of filters returned by filter_list() have any significance?
How can you determine if a specific filter is available on your PHP installation using filter_list()?
Can you retrieve additional information about each filter using filter_list()?
How do you use filter_list() to retrieve the names and IDs of the available filters?
Is it possible to add custom filters to the list returned by filter_list()?

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