PHP - como puedo combertir este codigo jQuery a PHP

jQuery(function($){

    function validateIdentificationNumber(number) {

        // Be sure to have something to test

        if (!number) {

            return false;

        }

        // Only take the first 11 characters

        number = number.substr(0, 11);

        // Test if we have well a 11-digit string

        if (!/\d{11}/.test(number)) {

            return false;

        }

        // Numbers we're going to check against

        var to_control = number.substr(0, 9);

        // Verification number

        var control = number.substr(9, 2);

        // Date parsing

        var date = number.substr(0, 6);

        var date_year = parseInt(date.substr(0, 2), 10);

        var date_month = parseInt(date.substr(2, 2), 10);

        var date_day = parseInt(date.substr(4, 2), 10);

        var today_year = parseInt(new Date().getFullYear().toString().substr(2, 2), 10);

        // Simple date check

        if (date_month < 1 || date_month > 12 || date_day < 1 || date_day > 31) {

            return false;

        }

        // Add '2' before if date after 1st Jan 2000

        if (date_year < today_year) {

            to_control = '2' + to_control.toString();

        }

        // Modulo calculation

        to_control = parseInt(to_control, 10);

        var modulo = 97 - (to_control % 97);

        modulo = Math.floor(modulo);

        modulo = modulo < 10 ? '0' + modulo : '' + modulo;

        // Final test

        return control === modulo;

    }

    $('#id_validator').submit(function(event){

        event.preventDefault();

        var input = $('#id_number').val();

        var valid = validateIdentificationNumber(input);

        $('#validity').text(valid ? 'valid' : 'invalid');

    });

})