filter_id() function in PHP

The filter_id() function returns the filter ID of a provided filter name. This is useful when you need to work with filter IDs directly or verify that a filter exists.

Syntax

filter_id(filtername)

Parameters

• filtername − The name of filter to get the ID from.

Return Value

The filter_id() function returns filter ID on success or FALSE, if the filter does not exist.

Example

Here's how to get filter IDs for all available filters ?

<?php
    foreach (filter_list() as $id => $filter) {
        echo $filter . " = " . filter_id($filter) . "<br>";
    }
?>

int = 257
boolean = 258
float = 259
validate_regexp = 272
validate_domain = 277
validate_url = 273
validate_email = 274
validate_ip = 275
validate_mac = 276
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

Checking Specific Filters

You can also check if a specific filter exists and get its ID ?

<?php
    $filter_name = "validate_email";
    $filter_id = filter_id($filter_name);
    
    if ($filter_id !== false) {
        echo "Filter '$filter_name' has ID: $filter_id<br>";
    } else {
        echo "Filter '$filter_name' does not exist<br>";
    }
    
    // Test with non-existent filter
    $invalid_filter = filter_id("non_existent_filter");
    var_dump($invalid_filter);
?>

Filter 'validate_email' has ID: 274
bool(false)

Conclusion

The filter_id() function is helpful for converting filter names to their corresponding numeric IDs. It returns FALSE for non-existent filters, making it useful for validation checks.