How can multiple dependent dropdown menus be implemented in PHP?

To implement multiple dependent dropdown menus in PHP, you can use AJAX to dynamically load the options for the second dropdown based on the selection in the first dropdown. This can be achieved by creating an AJAX request that fetches the options for the second dropdown based on the selected value from the first dropdown. 

<?php
// First Dropdown
echo "<select id='first_dropdown' onchange='getSecondDropdownOptions()'>";
echo "<option value='1'>Option 1</option>";
echo "<option value='2'>Option 2</option>";
echo "</select>";

// Second Dropdown
echo "<select id='second_dropdown'>";
echo "</select>";

// AJAX script
echo "<script>
function getSecondDropdownOptions() {
    var selectedValue = document.getElementById('first_dropdown').value;
    var xhr = new XMLHttpRequest();
    xhr.open('GET', 'get_options.php?selectedValue=' + selectedValue, true);
    xhr.onload = function() {
        if (xhr.status === 200) {
            var options = JSON.parse(xhr.responseText);
            var dropdown = document.getElementById('second_dropdown');
            dropdown.innerHTML = '';
            options.forEach(function(option) {
                var optionElement = document.createElement('option');
                optionElement.value = option.value;
                optionElement.textContent = option.label;
                dropdown.appendChild(optionElement);
            });
        }
    };
    xhr.send();
}
</script>";
?>

Keywords

PHP dependent dropdown menus AJAX JSON dynamic form interactions

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