JSFiddle - React, Tailwind, and code Playground

HTML

<select class="select first" data-type="1">
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>

<select class="select second hide" data-type="2">
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>

<select class="select third hide" data-type="3">
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
</select>
<br/><br/><br/>
<p class="result"></p>

CSS

.hide {
    display: none
}

JavaScript

$(document).ready(function(){    
    $('select.select').on('change', function(){
        var self = $(this),
            value = self.val(), // selected value
            dataType = self.data('type'); // Select type (1st, 2nd and 3rd)
        
        // Hide select third if change the first
        if (dataType == 1 && !$('.second').hasClass('hide') && !$('.third').hasClass('hide'))
        {
            $('.third').addClass('hide');
        // Show second select if hidden
        } else if (dataType == 1 && $('.second').hasClass('hide')) {
            $('.second').removeClass('hide');
        // Show third select if hidden
        } else if(dataType == 2 && $('.third').hasClass('hide')) {
            $('.third').removeClass('hide');
        }
        
        // function to call to get the values from php
        var valueText = getTheValueIntoPHPfile(value, dataType);
        $('p.result').html(valueText);
    })

    // On page load automatic select the first option value of the first select
    var f = $('select.first option:first-child');
    f.val(f.val()).trigger('change');
});

function getTheValueIntoPHPfile(value, dataType)
{
    return 'Value: ' + value + 
            '<br/>Select Type: ' + dataType;
    
    // Put your jquery request to PHP here and return the values to the next select
}