PHP: Regex to replace dash only if there are specific word and number before it

I am trying to replace a dash between two time values and replace it with the word to but only if before the first time value there is the word from

This is what I have until now, which works fine, but it matches all the cases where there are two timeframes with a dash between them.

$text = "The Spa center works 08:00-20:30 every day";
$text = preg_replace('/(\d{1,2})\-(\d{1,2})/','$1 to $2', $text);

And what I want it to trigger only if the sentence looks like that

The Spa center works from 08:00-20:30 every day

So the desired result should be

The Spa center works from 08:00 to 20:30 every day

>Solution :

You can use

preg_replace('/\bfrom\s+\d{1,2}:\d{2}\K-(?=\d{1,2}:\d{2}(?!\d))/',' to ', $text)

See the regex demo

Details:

• \b – a word boundary
• from – a word from
• \s+ – one or more whitespace
• \d{1,2}:\d{2} – one or two digits, :, two digits
• \K – omit the matched text
• - – a hyphen
• (?=\d{1,2}:\d{2}(?!\d)) – immediately on the right, there must be one or two digits, :, two digits not followed with another digit.