Parse a block of text containing square braced "tags" to produce a grouped 2d array

Question

I want to create grouped data in an array from the following string.

[car]Ford[/car]
[car]Dodge[/car]
[car]Chevrolet[/car]
[car]Corvette[/car]
[motorcycle]Yamaha[/motorcycle]
[motorcycle]Ducati[/motorcycle]
[motorcycle]Gilera[/motorcycle]
[motorcycle]Kawasaki[/motorcycle]

The result should be:

array(
    'car' => array(
        'Ford',
        'Dodge',
        'Chevrolet',
        'Corvette'
    ),
    'motorcycle' => array(
        'Yamaha',
        'Ducati',
        'Gilera',
        'Kawasaki'
    )
);

Answer 1

There are many ways to convert the information in this string to an associative array.

split the string on the new line into an array using the explode function:

$str = "[car]Ford[/car]
[car]Dodge[/car]
[car]Chevrolet[/car]
[car]Corvette[/car]
[motorcycle]Yamaha[/motorcycle]
[motorcycle]Ducati[/motorcycle]
[motorcycle]Gilera[/motorcycle]
[motorcycle]Kawasaki[/motorcycle]";

$items = explode(PHP_EOL, $str);

At this point each delimited item is now an array entry.

Array
(
    [0] => [car]Ford[/car]
    [1] => [car]Dodge[/car]
    [2] => [car]Chevrolet[/car]
    [3] => [car]Corvette[/car]
    [4] => [motorcycle]Yamaha[/motorcycle]
    [5] => [motorcycle]Ducati[/motorcycle]
    [6] => [motorcycle]Gilera[/motorcycle]
    [7] => [motorcycle]Kawasaki[/motorcycle]
)

Next, loop over the array and pull out the appropriate pieces needed to build the final associative array using the preg_match function with a regular expression:

$finalArray = [];
foreach($items as $item)
{
    //Use preg_match to capture the pieces of the string we want using a regular expression.
    //The first capture will grab the text of the tag itself.
    //The second capture will grab the text between the opening and closing tag.
    //The resulting captures are placed into the matches array.
    preg_match("/\[(.*?)\](.*?)\[/", $item, $matches);

    //Build the final array structure.
    $finalArray[$matches[1]] = $matches[2]
}

The following is an example of what will be found in the matches array for a given iteration of the foreach loop.

Array
(
    [0] => [motorcycle]Gilera[
    [1] => motorcycle
    [2] => Gilera
)

Please note that I use the PHP_EOL constant to explode the initial string. This may not work if the string was pulled from a different operating system than the one you are running this code on. You may need to replace this with the actual end of line characters that is being used by the string.