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

PHP Filters: validation and sanitization reference

Use validation filters when you need to decide whether data matches a required format. Sanitization changes data and is not a substitute for output escaping or prepared SQL statements.

$filters = filter_list();
foreach ($filters as $name) {
    echo $name . ' => ' . filter_id($name) . PHP_EOL;
}

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 )

$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>$key => $val <br>

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.

$ar=filter_list();<br>
foreach ($ar as $key => $val) {
echo "$key -> $val : ( ".filter_id($val). " ) &lt;br&gt;";
}

The output is here

$key -> $val : ( 257 ) <br>$key -> $val : ( 258 ) <br>$key -> $val : ( 259 ) <br>$key -> $val : ( 272 ) <br>$key -> $val : ( 277 ) <br>$key -> $val : ( 273 ) <br>$key -> $val : ( 274 ) <br>$key -> $val : ( 275 ) <br>$key -> $val : ( 276 ) <br>$key -> $val : ( 513 ) <br>$key -> $val : ( 513 ) <br>$key -> $val : ( 514 ) <br>$key -> $val : ( 515 ) <br>$key -> $val : ( 522 ) <br>$key -> $val : ( 516 ) <br>$key -> $val : ( 517 ) <br>$key -> $val : ( 518 ) <br>$key -> $val : ( 519 ) <br>$key -> $val : ( 520 ) <br>$key -> $val : ( 523 ) <br>$key -> $val : ( 1024 ) <br>

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 (deprecated): legacy reference 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()?

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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