Someone

<?php
        foreach ($residencies as $id=>$desc) {
?>

<option value="<?= $id ?>" <?= ($residency==$id) ? 'selected' : '' ?>> <?= $desc ?> </option>

<?php
        }
?>

<xar:foreach in="$residencies" key="$id" value="$desc">
        <option value="$id" <xar:if condition="$residency eq $id">'selected'<xar:else />''</xar:if>>
                $desc 
        </option>
</xar:foreach>