This is how array params or return types should be doc-blocked. The same goes if the arrays are keyed or not.

arrayDocBlocks.php

/**
 * @param int[] $theParam
 * @return int[]
 */
function ints(array $theParam): array
{
    return [
        1,
        2,
        3,
    ];
}

/**
 * @param float[] $theParam
 * @return float[]
 */
function floats(array $theParam): array
{
    return [
        0.1,
        1.2,
        3.14,
    ];
}

/**
 * @param bool[] $theParam
 * @return bool[]
 */
function bools(array $theParam): array
{
    return [
        true,
        false,
        true,
    ];
}

/**
 * @param string[] $theParam
 * @return string[]
 */
function strings(array $theParam): array
{
    return [
        'peter',
        'quagmire',
        'joe',
        'cleveland',
    ];
}

/**
 * @param mixed[] $theParam
 * @return mixed[]
 */
function mixed(array $theParam): array
{
    return [
        null,
        1,
        'mike',
        true,
        1.2,
        new stdClass(),
        ['mike'],
    ];
}

/**
 * @param array[] $theParam
 * @return array[]
 */
function arrays(array $theParam): array
{
    return [
        [],
        [],
        [],
    ];
}

/**
 * @param stdClass[] $theParam
 * @return stdClass[]
 */
function classes(array $theParam): array
{
    return [
        new stdClass(),
        new stdClass(),
        new stdClass(),
    ];
}

/**
 * @param mixed[][] $theParam
 * @return mixed[][]
 */
function nested(array $theParam): array
{
    return [
        ['id' => 1, 'name' => 'peter'],
        ['id' => 2, 'name' => 'quagmire'],
        ['id' => 3, 'name' => 'joe'],
        ['id' => 4, 'name' => 'cleveland'],
    ];
}