How can the default selection in a dropdown menu be set to empty when no option is chosen in a PHP form?

When no option is chosen in a dropdown menu in a PHP form, the default selection can be set to empty by adding an empty option at the top of the dropdown menu. This way, the user will have to actively select an option from the dropdown menu, instead of having a default option selected automatically. 

<select name="dropdown">
    <option value="">Choose an option</option>
    <option value="option1">Option 1</option>
    <option value="option2">Option 2</option>
    <option value="option3">Option 3</option>
</select>

Keywords

PHP dropdown menu default selection empty form

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