"Division by zero"/ NULL values TF-IDF - php

Question

I'm trying to test tf-idf package from PHP-ML, I tried using their documentation code but it keeps giving me "Division by zero" when I try to use different samples(strings).
use Phpml\FeatureExtraction\TfIdfTransformer;
$samples = [
["Tareq", "Tareq", "Tareq"],
["Mohammad", "Ahmad", "Tareq"]
];
$transformer = new TfIdfTransformer($samples);
dd($transformer);
And when I try using transform method from the example provide in their docs
$samples = [
[1, 2, 4],
[0, 2, 1]
];
$transformer = new TfIdfTransformer($samples);
$transformer->fit($samples);
dd($transformer->transform($samples));
it gives me NULL.
Tfdftransformer.php :
<?php
declare(strict_types=1);
namespace Phpml\FeatureExtraction;
use Phpml\Transformer;
class TfIdfTransformer implements Transformer
{
/**
* #var array
*/
private $idf = [];
public function __construct(array $samples = [])
{
if (count($samples) > 0) {
$this->fit($samples);
}
}
public function fit(array $samples, ?array $targets = null): void
{
$this->countTokensFrequency($samples);
$count = count($samples);
foreach ($this->idf as &$value) {
$value = log((float) ($count / $value), 10.0);
}
}
public function transform(array &$samples): void
{
foreach ($samples as &$sample) {
foreach ($sample as $index => &$feature) {
$feature *= $this->idf[$index];
}
}
}
private function countTokensFrequency(array $samples): void
{
$this->idf = array_fill_keys(array_keys($samples[0]), 0);
foreach ($samples as $sample) {
foreach ($sample as $index => $count) {
if ($count > 0) {
++$this->idf[$index];
}
}
}
}
}