PHP challenge

quine.php

<?php
$y = "function q(\$q) {
	\$q = str_replace('\\\\', '\\\\\\\\', \$q);
	\$q = str_replace('\$', '\\\\\$', \$q);
	\$q = str_replace('\\n', '\\\\n', \$q);
	\$q = str_replace('\"', '\\\\\"', \$q);
         return \$q;
}

echo \"<?php\\n\";
echo '\$y = \"' . q(\$y) . '\";';
echo \"\\n\\neval(\";
echo '\$y);';
echo \"\\n?>\\n\";
";

eval($y);
?>

My attempt at a PHP quine after seeing one by Trevor Sayre:
<?php printf($a='<?php printf($a=%c%s%c,39,$a,39);',39,$a,39);