мб так?

$text=preg_replace( \"/\\\\\\/\",\'\\\',$text);
$text=str_replace(\"\\r\\n\",\'<br>\', $text);
$text=str_replace(\"\\n\\n\",\'<p>\',$text);
$text=str_replace(\"\\n\",\'<br>\',$text);
$text=str_replace(\"\\t\",\' \',$text);
$text=str_replace(\"\\r\",\' \',$text);
$text=str_replace(\' \',\' \',$text);