What are some potential reasons for the problem of options being appended in PHP select boxes?

The problem of options being appended in PHP select boxes can occur when the code responsible for generating the select options is not properly resetting or clearing the options before adding new ones. To solve this issue, make sure to clear the select box options before adding new ones by either setting the select box innerHTML to an empty string or using a loop to remove each option individually.

// Clear select box options before adding new ones
echo '<select name="example_select">';
echo '<option value="">Select an option</option>';
// Clearing options by setting innerHTML to an empty string
echo '</select>';