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@ 2020-07-09T05:25:14Z

<?php

function flatten($array, $prefix = '') {
    $return = [];
    foreach ($array as $key => $value) {
        if (is_array($value)) {
            $return = array_merge($return, flatten($value, $prefix . $key . '_'));
        } else {
            $return[$prefix . $key] = $value;
        }
    }
    return $return;
}


// proof that it's working on the simple cases
var_dump(flatten([
    1, 2, 3 => [4, 5]
]));
var_dump(flatten([
    [1, 2], [3, 4]
])); // use array_values on the result if you don't care about keys

// simple multidimensional array
var_dump(flatten([
    'a' => [
        'b' => 'value',
    ]
]));

// proof that it's not overwriting values like all the other solutions
var_dump(flatten([
    'a' => [
        'b' => 'value',
    ],
    'c' => [
        'b' => 'anothervalue',
    ],
]));

Output for git.master, git.master_jit, rfc.property-hooks: array(4) { [0]=> int(1) [1]=> int(2) ["3_0"]=> int(4) ["3_1"]=> int(5) } array(4) { ["0_0"]=> int(1) ["0_1"]=> int(2) ["1_0"]=> int(3) ["1_1"]=> int(4) } array(1) { ["a_b"]=> string(5) "value" } array(2) { ["a_b"]=> string(5) "value" ["c_b"]=> string(12) "anothervalue" }

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Once feature-branches are merged or declined, they are no longer available. Their functionality (when merged) can be viewed from the main output page

2020-03-21 RFC: Is_Literal - declined
2020-12-04 Enumerations - included in PHP 8.1
2018-06-15 Typed Properties v2 - implemented in PHP 7.4
2016-08-12 Object typehint - included in PHP 7.2
2016-08-14 Arrow functions - withdrawn
2016-05-29 array_change_keys() - withdrawn
2016-04-19 Lexical scope support for anonymous classes - suspended
2016-04-17 Functional Interfaces - declined
2016-03-16 Typed Properties - superseded in favor of Typed Properties 2.0
2015-08-27 Callable Prototypes - declined
2015-05-01 Short Closures - declined / withdrawn in favor of Arrow Functions
2015-02-18 Scalar type hints v5 - included in PHP 7
2015-02-14 Union Types - declined
2013-09-22 Anonymous classes - included in PHP 7

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