PHP - MYSQL BACKUP

<?php

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "binax";

$conn = mysqli_connect($servername, $username, $password, $dbname) or die("Connection failed: " . mysqli_connect_error());
/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}


$tables = array();

$result = mysqli_query($conn,"SHOW TABLES");
while ($row = mysqli_fetch_row($result)) {
    $tables[] = $row[0];
}

$return = '';

foreach ($tables as $table) {
    $result = mysqli_query($conn, "SELECT * FROM ".$table);
    $num_fields = mysqli_num_fields($result);

    $return .= 'DROP TABLE '.$table.';';
    $row2 = mysqli_fetch_row(mysqli_query($conn, 'SHOW CREATE TABLE '.$table));
    $return .= "\n\n".$row2[1].";\n\n";

    for ($i=0; $i < $num_fields; $i++) {
        while ($row = mysqli_fetch_row($result)) {
            $return .= 'INSERT INTO '.$table.' VALUES(';
            for ($j=0; $j < $num_fields; $j++) {
                $row[$j] = addslashes($row[$j]);
                if (isset($row[$j])) {
                    $return .= '"'.$row[$j].'"';} else { $return .= '""';}
                    if($j<$num_fields-1){ $return .= ','; }
                }
                $return .= ");\n";
            }
        }
        $return .= "\n\n\n";

}


$handle = fopen('backup/backup.sql', 'w+');
fwrite($handle, $return);
fclose($handle);
echo "success";


?>