<?php
	$str = 'This is S3F8G m7j34m h98H40D-3D39 90843-432423 LSDF3 4X4it very good 343c3.';;
	preg_match_all("/(^[\D]+\s|\s[\D]+\s|\s[\D]+$|^[\D]+$)+/",$str,$result);
	$result = implode('',$result[0]);
	echo $result;