如何使用 PHP 从 json 数组中获取特定数量的项目

Question

I have a json document with the US states, in this form:

[
    {
        "name" : "Alabama",
        "abbreviation" : "AL"
    },
    {
        "name" : "Alaska",
        "abbreviation" : "AK"
    },
    {
        "name" : "Arizona",
        "abbreviation" : "AZ"
    },
    {
        "name" : "Arkansas",
        "abbreviation" : "AR"
    },
    {
        "name" : "California",
        "abbreviation" : "CA"
    },
    {
        "name" : "Colorado",
        "abbreviation" : "CO"
    },
    {
        "name" : "Connecticut",
        "abbreviation" : "CT"
    },
    {
        "name" : "Delaware",
        "abbreviation" : "DE"
    }
]

What I did is to decode the json document, then split the smaller arrays in their respective elements, by name and abbreviation. It echos the whole list of arrays properly.

$arrays = json_decode(file_get_contents('states.json'));
foreach ($arrays as $array) {
    $state_name = $array->{'name'};
    $state_abbreviation = $array->{'abbreviation'};
    echo '<p>' . $state_name . ' abbreviates ' . $state_abbreviation . '</p>';
}

But I need to be able to generate a specific number of random arrays from the big array which is the json file. Tried array_rand and there was no result. If the list has more than 50 items, from what I've read, mt_rand would be appropiate, because it might be faster and randomizes better. Only I didn't find too much info on mt_rand, except for numeric arrays.

How do I generate only 4, for example?

Thanks in advance!

And this is the solution with a small twist (slice factor), provided by @EinLinuus . Thanks, EinLinuus & Michel .

$arrays = json_decode(file_get_contents('states.json'));
shuffle($arrays);
$slice_factor = 4;
$arrays = array_slice($arrays, 0, $slice_factor);
foreach ($arrays as $array) {
    $state_name = $array->{'name'};
    $state_abbreviation = $array->{'abbreviation'};
    echo '<p>' . $state_name . ' abbreviates ' . $state_abbreviation . '</p>';
}

Answer 1

If you have your array stored in the variable $array , first shuffle the array with shuffle($array) . Now you have a random array and you can get the first x elements with array_slice($array, 0, x) ;

Example:

$array = [0, 1, 2, 3, 4, 5, 6]; // Your array
shuffle($array); // Shuffle the array, it could be now [4, 1, 6, 2, 5, 0, 3]
$result = array_slice($array, 0, 3); // Get first 3 elements, in this case [4, 1, 6];

Answer 2

You can also use the array_rand function to get randomly selected elements from the array.No shuffling or slicing.

$arr = range( 1, 20 );
$pick_random_items = 4;
$randoms = array_rand( $arr, $pick_random_items );