<?php
$que = "aa bb33cc 5.po";
echo preg_replace('/(?<=[^0-9,. ])(?=[0-9,.])|(?<=[0-9,.])(?=[^0-9,. ])/',' ',$que) . PHP_EOL;
echo preg_replace('/(?|([^0-9,. ])([0-9,.])|([0-9,.])([^0-9,. ]))/','$1 $2',$que) . PHP_EOL;
echo preg_replace('/(?:([^0-9,. ])([0-9,.])|([0-9,.])([^0-9,. ]))/','$1$3 $2$4',$que);
preferences:
28.44 ms | 404 KiB | 5 Q