php - preg_split() with multiple patterns not splitting quoted string

Question

I need to split a paragraph into sentences. That's where i got a bit confused with the regex.

I have already referred this question to which this Q is marked as a duplicate to. but the issue here is different.

Here is a example of the string i need to split :

hello! how are you? how is life
live life, live free. "isnt it?"

here is the code i tried :

$sentence_array = preg_split('/([.!?\r\n|\r|\n])+(?![^"]*")/', $paragraph, -1);

What i need is :

array (  
  [0] => "hello"  
  [1] => "how are you"  
  [2] => "how is life"  
  [3] => "live life, live free"  
  [4] => ""isnt it?""  
)

What i get is :

array(
  [0] => "hello! how are you? how is life live life, live free. "isnt it?""
)

When i do not have any quotes in the string, the split works as required.

Any help is appreciated. Thank you.

Possible duplicate of Explode a paragraph into sentences in PHP — H2ONOCK
– H2ONOCK, Commented Sep 28, 2018 at 8:10
You might try something like '~"[^"]*"(*SKIP)(*F)|\s*[.!?\r\n]\s*~', see demo. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 28, 2018 at 8:11
@H2ONOCK i had seen that one. but my issue here is specific and different. I have the split working fine without quotation marks. — Prashanth Benny
– Prashanth Benny, Commented Sep 28, 2018 at 8:14

revo · Accepted Answer · 2018-09-28 08:45:45Z

2

There are some problems with your regular expression that the main of them is confusing group constructs with character classes. A pipe | in a character class means a | literally. It doesn't have any special meaning.

What you need is this:

("[^"]*")|[!?.]+\s*|\R+

This first tries to match a string enclosed in double quotation marks (and captures the content). Then tries to match any punctuation marks from [!?.] set to split on them. Then goes for any kind of newline characters if found.

PHP:

var_dump(preg_split('~("[^"]*")|[!?.]+\s*|\R+~', <<<STR
hello! how are you? how is life
live life, live free. "isnt it?"
STR
, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY));

Output:

array(5) {
  [0]=>
  string(5) "hello"
  [1]=>
  string(11) "how are you"
  [2]=>
  string(11) "how is life"
  [3]=>
  string(20) "live life, live free"
  [4]=>
  string(10) ""isnt it?""
}

answered Sep 28, 2018 at 8:45

revo

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5 Comments

Prashanth Benny Over a year ago

thats a great solution... Thank you :)

Prashanth Benny Over a year ago

i have a little doubt here. can i use it for all UTF-8 strings? When i used it over Hindi text, it creates a � character when it finds अ and breaks(splits right there). any idea?

revo Over a year ago

Try to enable u flag i.e. ~("[^"]*")|[!?.]+\s*|\R+~u

Prashanth Benny Over a year ago

You just saved a day for me... you are a genius! :)

Prashanth Benny Over a year ago

i have a small query here. How do we ignore parentheses( ) as well? I have tried this |(\([^"]*\)). didn't help!

Tim Biegeleisen · Accepted Answer · 2018-09-28 08:37:26Z

1

I view your problem of splitting based on certain punctuation already solved, except that it fails in the case of double quotes. We can phrase a solution as saying that we should split when seeing such punctuation, or when seeing this punctuation followed by a double quote.

The split should happen when the previous character matches one of your markers and what follows is not a double quote, or the previous two characters should be a marker and a double quote. This implies splitting on the following pattern, which uses lookarounds:

(?<=[.!?\r\n])(?=[^"])|(?<=[.!?\r\n]")(?=.)

Code sample:

$input = "hello! how \"are\" \"you?\" how is life\nlive life, live free. \"isnt it?\"";
$sentence_array = preg_split('/(?<=[.!?\r\n])(?=[^"])|(?<=[.!?\r\n]\")(?=.)/', $input, -1);
print_r($sentence_array);

Array ( [0] => hello! [1] => how "are" "you?" [2] => how is life
    [3] => live life, live free. [4] => "isnt it?" )

edited Sep 28, 2018 at 8:37

answered Sep 28, 2018 at 8:16

Tim Biegeleisen

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3 Comments

Wiktor Stribiżew Over a year ago

OP wants to match sentence end punctuation outside of "s. Lookarounds won't help, your solution will fail in many cases.

Prashanth Benny Over a year ago

I have a small issue here, the \r\n, \r and \n are still in the string now. everything else is great. thank you Tim.

Tim Biegeleisen Over a year ago

I don't have a fix for that. I can only suggest removing them afterwards. The lookaround trick I used does not consume anything, this is why it leaves the double quotes untouched. But this also means that newlines/carriage returns would also not be removed.

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