How can PHP developers ensure their code is clean and efficient when counting unique values in an array?

To ensure clean and efficient code when counting unique values in an array, PHP developers can use the array_count_values() function to get the count of each value in the array, and then filter the resulting array to only include values with a count of 1. This approach avoids unnecessary loops and ensures accurate counting of unique values.

// Sample array
$array = [1, 2, 3, 2, 1, 4, 5, 4, 6];

// Get the count of each value in the array
$valueCounts = array_count_values($array);

// Filter the array to only include values with a count of 1
$uniqueValues = array_filter($valueCounts, function($count) {
    return $count == 1;
});

// Output the unique values
print_r(array_keys($uniqueValues));