How can chained select dropdown menus be implemented in PHP to create a hierarchical selection process?

Chained select dropdown menus can be implemented in PHP by using JavaScript to dynamically populate the dropdown menus based on the selection made in the previous dropdown. This allows for a hierarchical selection process where options are filtered based on the previous selection. 

<?php
// PHP code to generate the initial dropdown menu
echo "<select id='parent'>";
echo "<option value='1'>Option 1</option>";
echo "<option value='2'>Option 2</option>";
echo "</select>";

// JavaScript code to populate the child dropdown menu based on the selection in the parent dropdown
echo "<select id='child'></select>";
echo "<script>";
echo "
document.getElementById('parent').addEventListener('change', function() {
    var parentValue = this.value;
    var childDropdown = document.getElementById('child');
    childDropdown.innerHTML = '';

    if(parentValue == '1') {
        childDropdown.innerHTML += '<option value='1-1'>Child Option 1-1</option>';
        childDropdown.innerHTML += '<option value='1-2'>Child Option 1-2</option>';
    } else if(parentValue == '2') {
        childDropdown.innerHTML += '<option value='2-1'>Child Option 2-1</option>';
        childDropdown.innerHTML += '<option value='2-2'>Child Option 2-2</option>';
    }
});
";
echo "</script>";
?>

Keywords

PHP chained select dropdown menus hierarchical selection implementation

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