<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}
if ($result = $mysqli->query("SELECT * FROM City ORDER BY ID LIMIT 1")) {
    /* determine number of fields in result set */
    $field_cnt = $result->field_count;
    printf("Result set has %d fields.\n", $field_cnt);
    /* close result set */
    $result->close();
}
/* close connection */
$mysqli->close();
?>

<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}
if ($result = mysqli_query($link, "SELECT * FROM City ORDER BY ID LIMIT 1")) {
    /* determine number of fields in result set */
    $field_cnt = mysqli_num_fields($result);
    printf("Result set has %d fields.\n", $field_cnt);
    /* close result set */
    mysqli_free_result($result);
}
/* close connection */
mysqli_close($link);
?>

   

The above examples will output:

Result set has 5 fields.