PHP: remove from array of objects all duplicates by key, except first one

Question

I have the following associative array of objects:

[
    0: {
        "score": "value2",
        "number": "1",
        "finalScore": "-1"
    },

    1: {
        "score": "value3",
        "number": "2",
        "finalScore": "5"
    },

    2: {
        "score": "value4",
        "number": "2",
        "finalScore": "5"
    },

    3: {
        "score": "value5",
        "number": "3",
        "finalScore": "-1"
    }
]

Please, have in mind the following format is the prettified JSON string on the browser, after returning it from PHP through an echo json_encode($result)

I need to filter it based on the number property value, in order to remove all duplicates with the same value for the number property except the first one . This means that if two or more objects share the same value for number , only the first one should remain.

Given this explanation, the filtered array from the example above would result on:

[
    0: {
        "score": "value2",
        "number": "1",
        "finalScore": "-1"
    },

    1: {
        "score": "value3",
        "number": "2",
        "finalScore": "5"
    },

    2: {
        "score": "value5",
        "number": "3",
        "finalScore": "-1"
    }
]

I have made several attempts, the closest I've been is this funcion:

function array_iunique($array) {
    $lowered = array_map('strtolower', $array);
    return array_intersect_key($array, array_unique($lowered));
}

Answer 1

Sounds pretty straight forward to me: you iterate over the input array and accept the elements only if the output does not yet contain such a candidate...

<?php
$input = json_decode(<<<EOT
[
    {
        "score": "value2",
        "number": "1",
        "finalScore": "-1"
    }, {
        "score": "value3",
        "number": "2",
        "finalScore": "5"
    }, {
        "score": "value4",
        "number": "2",
        "finalScore": "5"
    }, {
        "score": "value5",
        "number": "3",
        "finalScore": "-1"
    }
]
EOT);

$output = [];
array_walk($input, function ($entry) use (&$output) {
    if (!array_key_exists($entry->number, $output)) {
        $output[$entry->number] = $entry;
    }
}); 

print_r(array_values($output));

The output obviously is:

Array
(
    [0] => stdClass Object
        (
            [score] => value2
            [number] => 1
            [finalScore] => -1
        )
    [1] => stdClass Object
        (
            [score] => value3
            [number] => 2
            [finalScore] => 5
        )
    [2] => stdClass Object
        (
            [score] => value5
            [number] => 3
            [finalScore] => -1
        )
)

Answer 2

Simple approache:

1. Firstly, convert data from json format to array of scores using json_decode with second args true .
   
2. Secondly, create three variable one for output $scores_filtered , second to keep track only unique numbers and $index to keep the order ascending of $scores_filtered array.
   
3. Thirdly, iterate over the array of score and check if the number first time occures (meaning doesn't exist in array $unique_numbers ) if So, store it in $unique_numbers . get that score and store in $scores_filtered array.

$json = '[{
        "score": "value2",
        "number": "1",
        "finalScore": "-1"
    },{
        "score": "value3",
        "number": "2",
        "finalScore": "5"
    },{
        "score": "value4",
        "number": "2",
        "finalScore": "5"
    },{
        "score": "value5",
        "number": "3",
        "finalScore": "-1"
    }
]';
$scores = json_decode($json, true);
$scores_filtered = [];
$unique_numbers = [];
$index = 0;
for($i = 0; $i < count($scores); $i++) {
    $score = $scores[$i];
    if(!in_array($score['number'], $unique_numbers)){
        $unique_numbers[] = $score['number'];
        $scores_filtered[$index]["score"] = $score["score"];
        $scores_filtered[$index]["number"] = $score["number"];
        $scores_filtered[$index]["finalScore"] = $score["finalScore"];
        $index += 1;
    }
}

Output:

echo "<pre>";
print_r(json_encode($scores_filtered, JSON_PRETTY_PRINT));
/*
[
    {
        "score": "value2",
        "number": "1",
        "finalScore": "-1"
    },
    {
        "score": "value3",
        "number": "2",
        "finalScore": "5"
    },
    {
        "score": "value5",
        "number": "3",
        "finalScore": "-1"
    }
]
*/