preg_split : splitting a string according to a very specific pattern

Question

Regex/PHP n00b here. I'm trying to use the PHP "preg_split" function...

I have strings that follow a very specific pattern according to which I want to split them.

Example of a string:

CADAVRES [FILM] (Canada : Québec, Érik Canuel, 2009, long métrage) FICTION

Desired result:

[0]CADAVRES
[1]FILM
[2]Canada : Québec
[3]Érik Canuel
[4]2009
[5]long métrage
[6]FICTION

Delimiters (in order of occurrence):

" ["
"] ("
", "
", "
", "
") "

How do I go about writing the regex correctly?

Here's what I've tried:

<?php
$pattern = "/\s\[/\]\s\(/,\s/,\s/,\s/\)\s/";
$string = "CADAVRES [FILM] (Canada : Québec, Érik Canuel, 2009, long métrage) FICTION";
$keywords = preg_split($pattern, $string);
print_r($keywords);

It's not working, and I don't understand what I'm doing wrong. Then again, I've just begun trying to deal with regex and PHP, so yeah... There are so many escape characters, I can't see right...

Thank you very much!

Do you want to obtain the list of delimiters as well? Or just the Desired Result part? — Robo Mop, Jan 18 '19 at 03:36
Avoid to use `preg_split` as its discontinued in latest version of PHP. — Naveed Ramzan, Jan 18 '19 at 03:42
@NaveedRamzan not according to the [PHP man page](http://php.net/manual/en/function.preg-split.php) it's not... — Nick, Jan 18 '19 at 04:11
@NaveedRamzan you mean split() perhaps? http://php.net/manual/en/function.split.php — Andreas, Jan 18 '19 at 04:27
@Nick: ah sorry, I was interested to say about `split()`. @Andreas: yes exactly :) thanks mate — Naveed Ramzan, Jan 18 '19 at 04:29
Why not just `\s*[][(),]\s*`? See live demo here https://3v4l.org/6YFkU — revo, Jan 18 '19 at 11:09
@NaveedRamzan, Nick, Andreas So split() is deprecated, but preg_split() is fine. Thanks! — Etienne Lehoux-Jobin, Jan 18 '19 at 19:28

score 3 · Answer 1 · answered Jan 18 '19 at 03:39

I managed to work out a solution using preg_match_all:

$input = "CADAVRES [FILM] (Canada : Québec, Érik Canuel, 2009, long métrage) FICTION";
preg_match_all("|[^-\\[\\](),/\\s]+(?:(?: :)? [^-\\[\\](),/]+)?|", $input, $matches);
print_r($matches[0]);

Array
(
    [0] => CADAVRES
    [1] => FILM
    [2] => Canada : Québec
    [3] => Érik Canuel
    [4] => 2009
    [5] => long métrage
    [6] => FICTION
)

The above regex considers a term as any character which is not something like bracket, comma, parenthesis, etc. It also allows for two word terms, possibly with a colon separator in the middle.

score 3 · Answer 2 · answered Jan 18 '19 at 04:08

You can use this regex to split on:

([^\w:]\s[^\w:]?|\s[^\w:])

It looks for a non-(word or :) character, followed by a space, followed by an optional non-(word or :) character; or a space followed by a non-(word or :) character. This will match all your desired split patterns. In PHP (note you need the u modifier to deal with unicode characters):

$input = "CADAVRES [FILM] (Canada : Québec, Érik Canuel, 2009, long métrage) FICTION";
$keywords = preg_split('/([^\w:]\s[^\w:]?|\s[^\w:])/u', $input);
print_r($keywords);

Output:

Array
(
    [0] => CADAVRES 
    [1] => FILM
    [2] => Canada : Québec
    [3] => Érik Canuel
    [4] => 2009
    [5] => long métrage
    [6] => FICTION
)

Demo on 3v4l.org

I don't know which one of our solutions is actually more brittle, but this is a very concise way of doing this +1. — Tim Biegeleisen, Jan 18 '19 at 04:22

ggorlen · Accepted Answer · 2019-01-18T04:44:05.613

Here's an attempt with preg_match:

$pattern = "/^([^\[]+)\[([^\]]+)\]\s+\(([^,]+),\s+([^,]+),\s+([^,]+),\s+([^,]+)\)\s+(.+)$/i";
$string = "CADAVRES [FILM] (Canada : Québec, Érik Canuel, 2009, long métrage) FICTION";
preg_match($pattern, $string, $keywords);
array_shift($keywords);
print_r($keywords);

Output:

Array
(
    [0] => CADAVRES 
    [1] => FILM
    [2] => Canada : Québec
    [3] => Érik Canuel
    [4] => 2009
    [5] => long métrage
    [6] => FICTION
)

Try it!

Regex breakdown:

^   anchor to start of string
 (    begin capture group 1
  [^\[]+   one or more non-left bracket characters
        )   end capture group 1
         \[   literal left bracket
           (   begin capture group 2
            [^\]]+   one or more non-right bracket characters
                  )    end capture group 2
                   \]   literal bracket
                     \s+    one or more spaces
                        \(    literal open parenthesis
                          (     open capture group 3
                           [^,]+   one or more non-comma characters
                                )     end capture group 3
                                 ,\s+     literal comma followed by one or more spaces
                                     ([^,]+),\s+([^,]+),\s+([^,]+)   repeats of the above
                                                                  \)   literal closing parenthesis
                                                                    \s+   one or more spaces
                                                                       (  begin capture group 7
                                                                        .+  everything else
                                                                           )  end capture group 7
                                                                            $ EOL

This assumes your structure to be static and is not particularly pretty, but on the other hand, should be robust to delimiters creeping into fields where they're not supposed to be. For example, the title having a : or , in it seems plausible and would break a "split on these delimiters anywhere"-type solution. For example,

"Matrix:, Trilogy()   [FILM, reviewed: good]    (Canada() :   Québec  ,  \t Érik Canuel , ): 2009 ,   long ():():[][]métrage) FICTIO  , [(:N";

correctly parses as:

Array
(
    [0] => Matrix:, Trilogy()   
    [1] => FILM, reviewed: good
    [2] => Canada() :   Québec  
    [3] => Érik Canuel 
    [4] => ): 2009 
    [5] => long ():():[][]métrage
    [6] => FICTIO  , [(:N
)

Try it!

Additionally, if your parenthesized comma region is variable length, you might want to extract that first and parse it, then handle the rest of the string.

preg_split : splitting a string according to a very specific pattern

3 Answers3