- array_push: documentation ( source)
- var_dump: documentation ( source)
- json_decode: documentation ( source)
- array_unique: documentation ( source)
<?php
$unflattened_array = [
'["2", "3"]',
'["4"]',
'["4", "3"]'
];
$flattened_array = [];
foreach ($unflattened_array as $items) {
array_push($flattened_array, ...json_decode($items));
}
$flattened_array = array_unique($flattened_array);
var_dump($flattened_array);