PHP: String to multidimensional array - php

Question

(Sorry for my bad English)
I have a string that I want to split into an array.
The corner brackets are multiple nested arrays.
Escaped characters should be preserved.
This is a sample string:
$string = '[[["Hello, \"how\" are you?","Good!",,,123]],,"ok"]'
The result structure should look like this:
array (
0 =>
array (
0 =>
array (
0 => 'Hello, \"how\" are you?',
1 => 'Good!',
2 => '',
3 => '',
4 => '123',
),
),
1 => '',
2 => 'ok',
)
I have tested it with:
$pattern = '/[^"\\]*(?:\\.[^"\\]*)*/s';
$return = preg_match_all($pattern, $string, null);
But this did not work properly. I do not understand these RegEx patterns (I found this in another example on this page).
I do not know whether preg_match_all is the correct command.
I hope someone can help me.
Many Thanks!!!

Answer 1

This is a tough one for a regex - but there is a hack answer to your question (apologies in advance).
The string is almost a valid array literal but for the ,,s. You can match those pairs and then convert to ,''s with
/,(?=,)/
Then you can eval that string into the output array you are looking for.
For example:
// input
$str1 = '[[["Hello, \\"how\\" are you?","Good!",,,123]],,"ok"]';
// replace , followed by , with ,'' with a regex
$pattern = '/,(?=,)/';
$replace = ",''";
$str2 = preg_replace($pattern, $replace, $str1);
// eval updated string
$arr = eval("return $str2;");
var_dump($arr);
I get this:
array(3) {
[0]=>
array(1) {
[0]=>
array(5) {
[0]=>
string(21) "Hello, "how" are you?"
[1]=>
string(5) "Good!"
[2]=>
string(0) ""
[3]=>
string(0) ""
[4]=>
int(123)
}
}
[1]=>
string(0) ""
[2]=>
string(2) "ok"
}
Edit
Noting the inherent dangers of eval the better option is to use json_decode with the code above e.g.:
// input
$str1 = '[[["Hello, \\"how\\" are you?","Good!",,,123]],,"ok"]';
// replace , followed by , with ,'' with a regex
$pattern = '/,(?=,)/';
$replace = ',""';
$str2 = preg_replace($pattern, $replace, $str1);
// eval updated string
$arr = json_decode($str2);
var_dump($arr);

Answer 2

If you can edit the code that serializes the data then it's a better idea to let the serialization be handled using json_encode & json_decode. No need to reinvent the wheel on this one.
Nice cat btw.

Answer 3

You might want to use a lexer in combination with a recursive function that actually builds the structure.
For your purpose, the following tokens have been used:
\[ # opening bracket
\] # closing bracket
".+?(?<!\\)" # " to ", making sure it's not escaped
,(?!,) # a comma, not followed by a comma
\d+ # at least one digit
,(?=,) # a comma followed by a comma
The rest is programming logic, see a demo on ideone.com. Inspired by this post.
class Lexer {
protected static $_terminals = array(
'~^(\[)~' => "T_OPEN",
'~^(\])~' => "T_CLOSE",
'~^(".+?(?<!\\\\)")~' => "T_ITEM",
'~^(,)(?!,)~' => "T_SEPARATOR",
'~^(\d+)~' => "T_NUMBER",
'~^(,)(?=,)~' => "T_EMPTY"
);
public static function run($line) {
$tokens = array();
$offset = 0;
while($offset < strlen($line)) {
$result = static::_match($line, $offset);
if($result === false) {
throw new Exception("Unable to parse line " . ($line+1) . ".");
}
$tokens[] = $result;
$offset += strlen($result['match']);
}
return static::_generate($tokens);
}
protected static function _match($line, $offset) {
$string = substr($line, $offset);
foreach(static::$_terminals as $pattern => $name) {
if(preg_match($pattern, $string, $matches)) {
return array(
'match' => $matches[1],
'token' => $name
);
}
}
return false;
}
// a recursive function to actually build the structure
protected static function _generate($arr=array(), $idx=0) {
$output = array();
$current = 0;
for($i=$idx;$i<count($arr);$i++) {
$type = $arr[$i]["token"];
$element = $arr[$i]["match"];
switch ($type) {
case 'T_OPEN':
list($out, $index) = static::_generate($arr, $i+1);
$output[] = $out;
$i = $index;
break;
case 'T_CLOSE':
return array($output, $i);
break;
case 'T_ITEM':
case 'T_NUMBER':
$output[] = $element;
break;
case 'T_EMPTY':
$output[] = "";
break;
}
}
return $output;
}
}
$input = '[[["Hello, \"how\" are you?","Good!",,,123]],,"ok"]';
$items = Lexer::run($input);
print_r($items);
?>