Implement a groupByOwners function that:

• Accepts an associative array containing the file owner name for each file name.
• Returns an associative array containing an array of file names for each owner name, in any order.

For example, for associative array ["Input.txt" => "Randy", "Code.py" => "Stan", "Output.txt" => "Randy"] the groupByOwners function should return ["Randy" => ["Input.txt", "Output.txt"], "Stan" => ["Code.py"]].

A palindrome is a word that reads the same backward or forward.

Write a function that checks if a given word is a palindrome. Character case should be ignored.

For example, isPalindrome("Deleveled") should return true as character case should be ignored, resulting in "deleveled", which is a palindrome since it reads the same backward and forward.

The user interface contains two types of user input controls: TextInput, which accepts all texts and NumericInput, which accepts only digits.

Implement the class TextInput that contains:

• Public function add($text) - adds the given text to the current value.
• Public function getValue() - returns the current value (string).

Implement the class NumericInput that:

• Inherits from TextInput.
• Overrides the add method so that each non-numeric text is ignored.

For example, the following code should output '10':

$input = new NumericInput();
$input->add('1');
$input->add('a');
$input->add('0');
echo $input->getValue();