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

Question

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

Final Solution

Thanks to @Wiktor Stribiżew help, the final solution, will match also Unicode and spaces between the two timeframes and the dash looks like that.

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

@WiktorStribiżew, this is also matching all the cases

lStoilov
– lStoilov

2023-01-23 12:13:28 +00:00
Commented Jan 23, 2023 at 12:13 — lStoilov
– lStoilov, Commented Jan 23, 2023 at 12:13

Wiktor Stribiżew · Accepted Answer · 2023-01-23 12:17:59Z

0

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.

edited Jan 23, 2023 at 12:17

answered Jan 23, 2023 at 12:15

Wiktor Stribiżew

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5 Comments

lStoilov Over a year ago

just one more question. If the word is not from, but another language that is Unicode? For example instead of from, to be от. How can I do that?

Wiktor Stribiżew Over a year ago

@lStoilov You will need a u flag, e.g. with Russian: '/\bс\s+\d{1,2}:\d{2}\K-(?=\d{1,2}:\d{2}(?!\d))/u'. Fortunately, word boundaries in PHP are Unicode-aware when the u flag is used.

lStoilov Over a year ago

I have tried that and it didn't work... But it was my bad... I had a typo. Now it worked correctly

lStoilov Over a year ago

one last question... what if the times are written with a space before and after the dash. Like this 08:00-20:30

Wiktor Stribiżew Over a year ago

@lStoilov '/\bс\s+\d{1,2}:\d{2}\s*\K-(?=\s*\d{1,2}:\d{2}(?!\d))/u'

Tim Biegeleisen · Accepted Answer · 2023-01-23 12:17:17Z

0

You may include the from keyword in your regex pattern:

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

edited Jan 23, 2023 at 12:17

answered Jan 23, 2023 at 12:12

Tim Biegeleisen

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2 Comments

lStoilov Over a year ago

This is working but also removes the word from. So it becomes The Spa center works 08:00 to 20:30 every day

Ted Lyngmo Over a year ago

You could capture from too since that should be in the output \b(from \d{1,2}:\d{2})-(\d{1,2}:\d{2})

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