I have this project about booking system in php. little bit old tbh but it's get the job done

Anyway.. I have a problem with the "datepicker" in jquery.

I have this input field

<div class="booking_dropdown"><input type="text" id="datepicker" class="datepicker" placeholder="Check in" name="arrival" required="required" value="<?php echo isset($_POST['arrival']) ? $_POST['arrival'] :date('m/d/Y');?>"></div>

with I connected with the datepicker function

here it's code

$('#datepicker').datepicker({
    inline: true,
    startDate: new Date(),
    changeMonth: true,
    changeYear: true,
    showButtonPanel: true,
    minDate: 0
});

the mineDate: 0 suppose to make the booking mechanism start from current day and disable all the past days, but actually the whole datepicker function turned out to be not working at all. idk why tbh

Note : the function located in another file called index.html and the input field located in file called template.php

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