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PHP input filtering for complex arrays

Posted by: admin July 12, 2020 Leave a comment


Official PHP documentation states that filter_var_array() supports array filtering in the following format:

$data = array(
    'testarray'    => array('2', '23', '10', '12')

$args = array(
    'testarray'    => array('filter'    => FILTER_VALIDATE_INT,
                            'flags'     => FILTER_FORCE_ARRAY

$myinputs = filter_var_array($data, $args);

However, if the array in question is multi-dimensional and requires different filters for different parts, how would you approach defining filtering options?

As an example:

$data = array(
    'testhash'    => array('level1'=>'email', 
                           'level2'=> array('23', '10', '12'))
How to&Answers:

Idea 1

Consider using FILTER_CALLBACK. In this way, you can write a callback function that itself uses the filter extension, thus providing a recursive ability.

function validate_array($args) {
    return function ($data) use ($args) {
        return filter_input_array($data, $args);

This will generate the callback functions.

$args = array(
    'user' => array(
        'filter' => FILTER_CALLBACK,
        'options' => validate_array(array(
            'age' => array('filter' => FILTER_INPUT_INT),
            'email' => array('filter' => FILTER_INPUT_EMAIL)

This is what the config array would then look like.

Idea 2

Do not hesitate to pat me on the back for this one because I am quite proud of it.

Take an arg array that looks like this. Slashes indicate depth.

$args = array(
    'user/age' => array('filter' => FILTER_INPUT_INT),
    'user/email' => array('filter' => FILTER_INPUT_EMAIL),
    'user/parent/age' => array('filter' => FILTER_INPUT_INT),
    'foo' => array('filter' => FILTER_INPUT_INT)

Assume your data looks something like this.

$data = array(
    'user' => array(
        'age' => 15,
        'email' => '[email protected]',
        'parent' => array(
            'age' => 38
    'foo' => 5

Then, you can generate an array of references that map keys such as ‘user/age’ to $data[‘user’][‘age’]. In final production, you get something like this:

function my_filter_array($data, $args) {
    $ref_map = array();
    foreach ($args as $key => $a) {
        $parts = explode('/', $key);
        $ref =& $data;
        foreach ($parts as $p) $ref =& $ref[$p];
        $ref_map[$key] =& $ref;
    return filter_var_array($ref_map, $args);

var_dump(my_filter_array($data, $args));

Now the only question is how you deal with the mismatch between the validation record and the original data set. This I cannot answer without knowing how you need to use them.