flattening array algo

<?php

$array = [
    ['a', 'b'],
    ['c', ['d','e']],
    'f',
    ['g']
];

function flattening_array(array $items, array &$flattened = [])
{
    foreach ($items as $item) {
        if( is_array($item) )
        {
            flattening_array($item, $flattened);
            continue;
        }
        $flattened[] = $item;
    }
}

$flat_array = [];
flattening_array($array,$flat_array);

print_r( $flat_array );

?>