preg_replace clips characters in string - php

Question

i have a string (part of a JSON data) and want to parse it in brackets [...]. here is the example :
For example
[-0.5937, 2.0734,-0.1577, 1.7941,0.2048, 1.5296] >>> [-0.5937, 2.0734], [-0.1577, 1.7941], [0.2048, 1.5296]
i wrote this PHP code works good but the problem is: when it finds the ',' and adding '], [' characters instead of it, deletes the some digits of coordinates. You can check it by adding 123456789 value after the coordinates. for example -0.5937 => -0.5937123456789 So how can i avoid deleting digits of coordinates ???
Example Code
<?php
$line = '[-0.5937, 2.0734,-0.1577, 1.7941,0.2048, 1.5296]';
$brackets = preg_replace('/\d,\S/', '], [', $line);
echo $brackets;
?>

Answer 1

You can do this:
$string = '[-0.5937, 2.0734,-0.1577, 1.7941,0.2048, 1.5296]';
$pattern = '~[[,]\s*(-?\d++(?>\.\d++)?)\s*,\s*(-?\d++(?>\.\d++)?)\s*(?:]|(?=(,)))~';
$result = preg_replace($pattern, '[$1, $2]$3 ', $string);
pattern details:
~ # pattern delimiter
[[,] # a [ or a ,
\s* # optional spaces
(-?\d++(?>\.\d++)?) # a number (group 1)
\s*,\s* # ,
(-?\d++(?>\.\d++)?) # (group 2)
\s*
(?: # non capturing group
] # literal ]
| # OR
(?=(,)) # a lookahead that capture the comma (group 3)
)
~

Answer 2

You can do this using an assertion to prevent the pattern from capturing the digit and the non-whitespace character. like so:
'/(?<=\d),(?<=\S)/'
Or, you can just change your pattern to:
'/,(?<=\S)/'
to ignore the digit character.
What I would recommend doing, however, would make your code not rely on the space before numbers. Use preg_replace_callback:
<?php
$line = '[-0.5937, 2.0734,-0.1577, 1.7941,0.2048, 1.5296]';
$i = 0;
function everyOther($matches) {
$i++;
if ($i % 2 == 1)
return ',';
else
return '], [';
}
$brackets = preg_replace_callback(
'/,/',
'everyOther',
$line);
echo $brackets;
?>
This will replace every other comma.