PHP export text into Excel can't see normal style as former

function change_excel_br($str){
    $new_str ="";
    if($str){
	    $p_new_lines   = array("\r\n", "\n", "\r","\r\n", "<pre>","</pre>","<br>","</br>","<br/>");  
		$p_change_line_in_excel_cell = '<br style="mso-data-placement:same-cell;" />';  
		$new_str = str_replace( $p_new_lines,$p_change_line_in_excel_cell,$str);  
	}
	return $new_str;
}