Search difference of 2 files

<?php

$file_big = "file-big.txt";
$file_small = "file-small.txt";
$file_clear = "file-clear.txt";

function getLines($file) {
	$f = fopen($file, 'r');
	try {
		while ($line = fgets($f)) {
			yield $line;
		}
	} finally {
		fclose($f);
	}
}


$arrBig = [];
$arrSmall = [];

foreach (getLines($file_big) as $line) {
	$clear_line = str_replace(array("\r","\n"), '', $line);
	array_push($arrBig, $clear_line);
}

foreach (getLines($file_small) as $line) {
	$clear_line = str_replace(array("\r","\n"), '', $line);
	array_push($arrSmall, $clear_line);
}

$result = array_diff($arrBig, $arrSmall);

foreach ($result as $item) :
	$content_to_write .= $item . PHP_EOL;
endforeach;


file_put_contents ($file_clear, $content_to_write, FILE_APPEND);