PHP preg_split() pattern - php

Question

I need help finding a PCRE pattern using preg_split().
I'm using the regex pattern below to split a string based on its starting 3 character code and semi-colons. The pattern works fine in Javascript, but now I need to use the pattern in PHP. I tried preg_split() but just getting back junk.
// Each group will begin with a three letter code, have three segments separated by a semi-colon. The string will not be terminated with a semi-colon.
// Pseudocode
string_to_split = "AAA;RED;111;BBB;BLUE;22;CCC;GREEN;33;DDD;WHITE;44"
// This works in JS
// https://regex101.com
$pattern = "/[AAA|BBB|CCC|DDD][^;]*;[^;]*[;][^;]*/gi";
Match 1
Full match 0-11 `AAA;RED;111`
Match 2
Full match 12-23 `BBB;BLUE;22`
Match 3
Full match 24-36 `CCC;GREEN;33`
Match 4
Full match 37-49 `DDD;WHITE;44`
$pattern = "/[AAA|BBB|CCC|DDD][^;]*;[^;]*[;][^;]*/";
$split = preg_split($pattern, $string_to_split);
returns
array(5)
0:""
1:";"
2:";"
3:";"
4:""

Answer 1

According to your additional information in some comments to the answers, I update my answer to be very specific to your source format.
You might want something like this:
$subject = "AAA;RED;111;AAA;Oh my dog;12.34;AAA;Oh Long John;.4556;BBB;Oh Long Johnson;1.2323;BBB;Oh Don Piano;.33;CCC;Why I eyes ya;1.445;CCC;All the live long day;2.3343;DDD;Faith Hilling;.89";
$pattern = '/(?<=;|^)(AAA|BBB|CCC|DDD);([^;]*);((?:\d*\.)?\d+)(?=;|$)/';
preg_match_all($pattern, $subject,$matches);
var_dump($matches);
giving you
array (size=4)
0 =>
array (size=8)
0 => string 'AAA;RED;111' (length=11)
1 => string 'AAA;Oh my dog;12.34' (length=19)
2 => string 'AAA;Oh Long John;.4556' (length=22)
3 => string 'BBB;Oh Long Johnson;1.2323' (length=26)
4 => string 'BBB;Oh Don Piano;.33' (length=20)
5 => string 'CCC;Why I eyes ya;1.445' (length=23)
6 => string 'CCC;All the live long day;2.3343' (length=32)
7 => string 'DDD;Faith Hilling;.89' (length=21)
1 =>
array (size=8)
0 => string 'AAA' (length=3)
1 => string 'AAA' (length=3)
2 => string 'AAA' (length=3)
3 => string 'BBB' (length=3)
4 => string 'BBB' (length=3)
5 => string 'CCC' (length=3)
6 => string 'CCC' (length=3)
7 => string 'DDD' (length=3)
2 =>
array (size=8)
0 => string 'RED' (length=3)
1 => string 'Oh my dog' (length=9)
2 => string 'Oh Long John' (length=12)
3 => string 'Oh Long Johnson' (length=15)
4 => string 'Oh Don Piano' (length=12)
5 => string 'Why I eyes ya' (length=13)
6 => string 'All the live long day' (length=21)
7 => string 'Faith Hilling' (length=13)
3 =>
array (size=8)
0 => string '111' (length=3)
1 => string '12.34' (length=5)
2 => string '.4556' (length=5)
3 => string '1.2323' (length=6)
4 => string '.33' (length=3)
5 => string '1.445' (length=5)
6 => string '2.3343' (length=6)
7 => string '.89' (length=3)
The start marker should occur at the start of string or immidiately after a semicolon, so we do a lookbehind, looking for start or semicolon:
(?<=;|^)
We look for an alternative of AAA,BBB,CCC or DDD and capture it:
(AAA|BBB|CCC|DDD)
After a semicolon we look for any character except a semicolon. The quantifier * means 0 or more time. Use + if you want at least 1.
;([^;]*)
After the next semicolon wie look for a number. This task has to be splitted to fit a valid format: We first look for 0 or more digits followed by a dot:
(?:\d*\.)?
where (?:) means a non-capturing group.
Behind we look for at least one digit: \d+
We want to capture both parts of of the number using parentheses after the searched semicolon:
;((?:\d*\.)?\d+)
This matches "1234", ".1234", "1.234", "12.34" , "123.4" but "1234.", "1.2.3"
Finally we want this to immediately occur before a semicolon or the end of string. Thus we do a lookahead:
(?=;|$)
Lookaheads and lookbehinds are not part of the captured result behind or respectively before.

Answer 2

I've modified your pattern a little, and added a couple of flags to preg_split.
The PREG_SPLIT_NO_EMPTY flag will exclude empty matches from the result, and PREG_SPLIT_DELIM_CAPTURE will include the captured value in the result.
$split = preg_split('/([abcd]{3};[^;]+;\d+);?/i', $string, -1, PREG_SPLIT_NO_EMPTY|PREG_SPLIT_DELIM_CAPTURE);
Result:
Array
(
[0] => AAA;RED;111
[1] => BBB;BLUE;22
[2] => CCC;GREEN;33
[3] => DDD;WHITE;44
)
Alternatively, and more suitably, you can use preg_match_all with the following pattern.
preg_match_all('/([abcd]{3};[^;]+;\d+);?/i', $string, $matches);
print_r($matches[0]);
Result:
Array
(
[0] => AAA;RED;111
[1] => BBB;BLUE;22
[2] => CCC;GREEN;33
[3] => DDD;WHITE;44
)

Answer 3

You don't want to split your string but match elements, use preg_match_all:
$str = "AAA;RED;111;AAA;Oh my dog;2.34;AAA;Oh Long John;.4556;BBB;Oh Long Johnson;1.2323;BBB;Oh Don Piano;.33;CCC;Why I eyes ya;1.445;CCC;All the live long day;2.3343;DDD;Faith Hilling;.89";
$res = preg_match_all('/(?:AAA|BBB|CCC|DDD);[^;]*;[^;]*;?/', $str, $m);
print_r($m[0]);
Output:
Array
(
[0] => AAA;RED;111;
[1] => AAA;Oh my dog;2.34;
[2] => AAA;Oh Long John;.4556;
[3] => BBB;Oh Long Johnson;1.2323;
[4] => BBB;Oh Don Piano;.33;
[5] => CCC;Why I eyes ya;1.445;
[6] => CCC;All the live long day;2.3343;
[7] => DDD;Faith Hilling;.89
)
Explanation:
/ : regex delimiter
(?:AAA|BBB|CCC|DDD) : non capture group AAA or BBB or CCC or DDD
; : a semicolon
[^;]* : 0 or more any character that is not a semicolon
; : a semicolon
[^;]* : 0 or more any character that is not a semicolon
;? : optional semicolon
/ : regex delimiter