Someone

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

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

<?php
        }
?>

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