Replace "." in the text

[sandy1028]

In the  text,

 

It will eventually go away.Once the carriers merge, the combined airline, will operate as Southwest. It has its logo and colors. 2.3 AirTran brand will no longer be used. 

 

In the above text, how to replace "." with ". "  and not in 2.3.

 

how to add space after "." only if it has alphabets and not to replace after numeric characters.

[ocpaul20]

some kind of pattern matching I assume but I am terrible at that. I tend to do it the long way with a for loop on the string rather than get my head around all the pattern matching syntax.

[jcbones]

<?php

$str = 'It will eventually go away.Once the carriers merge, the combined airline, will operate as Southwest. It has its logo and colors. 2.3 AirTran brand will no longer be used. ';

$patt = '~(\.)([^\d\s])~'; //select a period that is NOT followed by a numerical digit or a space (capturing the space in the 1st group, and the alpha character in the second group).

$str = preg_replace($patt,'$1 $2',$str); //replace the pattern with the 1st capture and the 2nd capture separated by a space.

echo $str;

?>

[xyph]

If it has to be a full stop, why would you capture it?