how to merge two models of regex patterns?

Question

Let's say I have a string.

`$str = "   Hi, my  name is 
         Petr"; `

Expecting: $str = " Hi, my name is Petr";

I need to replace all the white spaces '....' at the beginning of the string and then if there is a multiple number of white space between words in the string then replace it with one empty space.

I want to do this with the regex function 'preg_replace'.

But I don't know how to "/^\s+/" for remove white spaces on the start of string and "/\s+/" for white spaces between words in a string. Is it possible to merge the two formula patterns into one pattern? If so, what would the formula look like?

What do you want to do with the newline in the string? leave it intact? — Nick, Dec 09 '19 at 01:45
https://stackoverflow.com/questions/2326125/remove-multiple-whitespaces — sumit, Dec 09 '19 at 01:46
Let's say I apply these regexes to the array where the client's home address is included. @Nick — Petr Fořt Fru-Fru, Dec 09 '19 at 01:49

score 1 · Answer 1 · answered Dec 09 '19 at 01:47

1

I guess,

$str = '   Hi, my  name is
         Petr';
$result = preg_replace('/\s{2,}/', ' ', $str);
$result = preg_replace('/^\s*|\s*$/', '', $result);

echo $result;

might work OK, which'd output:

Hi, my name is Petr

answered Dec 09 '19 at 01:47

Emma

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score 1 · Accepted Answer · answered Dec 09 '19 at 01:50

1

There are a couple of ways to achieve this. You can take advantage of the fact that preg_replace can take an array of patterns and replacements to use your two regexes:

$str = "   Hi, my  name is 
         Petr";
echo preg_replace(array('/^\s+/', '/\s+/'), array('', ' '), $str) . "\n";

Alternatively, you can use a slightly more complicated regex using a positive lookbehind to remove any sequence of whitespace that is preceded by either the start of string (^) or other whitespace:

echo preg_replace('/(?<=^|\s)\s+/', '', $str);

In both cases the output is

Hi, my name is Petr
Hi, my name is Petr

Demo on 3v4l.org

answered Dec 09 '19 at 01:50

Nick

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Thank you for help. I will try both your methods. @Nick – Petr Fořt Fru-Fru Dec 09 '19 at 02:15
@PetrFořtFru-Fru no worries - but you shouldn't accept an answer until after you've had a chance to test it. – Nick Dec 09 '19 at 02:43
Do not worry. I've already tried both regexes. I used the easier method. So far I'm trying to understand regexes, I'm learning. Thanks again. @Nick – Petr Fořt Fru-Fru Dec 09 '19 at 02:59
Please, I still have a question about regex. Can this regex be applied in MariaDB SQL? MariaDB has a function REGEXP_REPLACE but probably I'm not good enough to write a functional regex for MariaDB. Thank you. @Nick – Petr Fořt Fru-Fru Dec 11 '19 at 09:55
1

@PetrFořtFru-Fru yes, you just need to use a nested `regexp_replace`, and escape the backslashes: https://dbfiddle.uk/?rdbms=mariadb_10.2&fiddle=143b6668305f42b0dc16266f84ee8372 – Nick Dec 11 '19 at 11:46

how to merge two models of regex patterns?

2 Answers2