Ignoring insert of first new line

Question

I am trying to read txt file, find $id and increment it's value $id=>value. But the problem is that when I want to save changes the first new line is ignored so

10=>26
30=>11
33=>22

became this after I run the script

10=>2730=>11
33=>22

This

10=>26
30=>11
33=>22

Should result in this

10=>27
30=>11
33=>22

Here is the code. I am using $id = 10.

 $tmp= "";
    $file = file_get_contents(dirname(__FILE__) . "/requests.txt", "r");
    $file = explode("\n", $file);
    foreach ($file as $product){

        $data = explode("=>", $product);
        if($data[0] == $id) {
            $data[1] += 1;
            $product = $data[0]."=>".$data[1];
            $tmp = $tmp.$product."\n";
            continue 1;
        }
        $tmp = $tmp.$product."\n";
    }
    echo $tmp;
    file_put_contents(dirname(__FILE__) . "/abc.txt", $tmp);