How to use array_diff for (.txt) files in PHP

Question

<?php
$new = array("12", "11", "10", "9", "8", "7", "6", "5", "4");
$old = array("10", "9", "8", "7", "6", "5", "4", "3", "2", "1");

$result = array_diff($new, $old);

print_r($result);
?>

The result is Array ( [0] => 12 [1] => 11 ) so 12 and 11

According to this example how to use array_diff for (.txt) files in PHP?

Here are (.txt) examples:

New (.txt) file

Something here12
Something here11
Something here10
Something here9
Something here8
Something here7
Something here6
Something here5
Something here4
Something here3

Old (.txt) file

Something here10
Something here9
Something here8
Something here7
Something here6
Something here5
Something here4
Something here3
Something here2
Something here1

Output (.txt) file

Something here12
Something here11

Answer 1

You just need to reproduce your arrays from the text files :

<?php
$new = explode(PHP_EOL, file_get_contents('new.txt').PHP_EOL);
$old = explode(PHP_EOL, file_get_contents('old.txt').PHP_EOL);
$result = array_diff($new, $old);

$output= fopen("Output.txt", "w") or die("Unable to open file!");
foreach($result as $value){
    fwrite($output, $value.PHP_EOL);
}

?>

I am not sure if you wanted the strip the "Something here" but in your exemple output.txt it seems like not.