Add header and footer to txt file generated via phptxt

Use an array to group the data in the correct sequence, then add everything with join() before writing to the file;

<?php
        while($data = mysql_fetch_array($querymail)) {
        $log = str_pad($data[0], 10, "0", STR_PAD_LEFT);
        $log1 = str_pad($data[1], 15, " ", STR_PAD_RIGHT);
        $log2 = str_pad($data[2], 10, "0", STR_PAD_LEFT);
                $log3 = str_pad($data[3], 10, "0", STR_PAD_LEFT);

        // Agrupe os valores num array ao invés de concatenar as strings, 
        // note o valor em branco na primeira posição
        $savelogs = array('', $cod3, $log, $log1, $log2, $cod4b, $cod5b, $cod6b, $log3, $cod7b, $cod8b);

        // pegue os totais que vai usar
        $totallivro = // total de livros;
        $valortotal = // total de livros;

        // Coloque a data na primeira posição do array
        array_unshift( $savelogs, date('dmYHs') );

        // Adicione mais uma linha em branco
        // e os totais ao final
        $savelogs[] = '';
        $savelogs[] = $totallivro.' '.$valortotal;

        // junte tudo numa string só
        $savelogs = join("\n", $savelogs);

        if (!$savelog = fopen('txt/relatorio.txt', "a")) 
        { exit; }        
        if (!fwrite($savelog, $savelogs."\r\n" ))
        { exit; fclose($savelog); }
        }

Use fwrite before while to write the header; during while you will accumulate any variables that you need to total, and at the end, after the end of while , you can use another fwrite to write the total values.

Note: Ideally, you should open the file only once, and only close after everything is written.