Not working on PHP 5.4

It is this bit of code, and most of the variables are not set:

$mediahtml .= <<<_end_
	<{$tagName} id="wp_mep_{$mediaElementPlayerIndex}" {$src_attribute} {$type_attribute} {$width_attribute} {$height_attribute} {$poster_attribute} controls="controls" {$preload_attribute} {$autoplay_attribute} $video_skin_attribute>
		{$mp4_source}
		{$mp3_source}
		{$webm_source}
		{$flv_source}
		{$wmv_source}
		{$ogg_source}
		{$captions_source}
		<object width="{$width}" height="{$height}" type="application/x-shockwave-flash" data="{$dir}flashmediaelement.swf">
			<param name="movie" value="{$dir}flashmediaelement.swf" />
			<param name="flashvars" value="controls=true&file={$flash_src}" />
		</object>
	</{$tagName}>
<script type="text/javascript">
jQuery(document).ready(function($) {
	$('#wp_mep_$mediaElementPlayerIndex').mediaelementplayer({
		m:1
		{$loop_option}
		{$controls_option}
		{$audio_size}
	});
});
</script>

_end_;

Until there is an update, I’m suppressing the errors with a horrible, horrible hack:

@$mediahtml .= @<<<_end_
        ...
_end_;

Note it requires TWO @s as both sides of the assignment have missing variables ($mediahtml does not exist, but is being appended to).