How to INSERT and UPDATE - php

Question

I've already checked here on stackoverflow and searched on google, but couldn't find my answer. I've created a rating system Thumbs up and down, only members could vote on a article. When a member votes, sql is updating the row voteup/votedown. Now I've made a new table called vote I've got there 5 columns id, user, uID, ctitle, cID
So If a member who is logged in as for ex: Admin and he thumbs up the article for ex: I like coding SQL INSERT INTO the table which is called vote Admin to user the title into ctitle but at the same time he needs to update the table called post the row vote_up or vote_down
I'm only receiving the error: Failed to vote,
<?php
include 'config.php';
require_once 'core/init.php';
$user = new User();
$username = $user->data()->username;
function getAllVotes(mysqli $db, $id)
{
$votes = array();
if($q_13 = "SELECT * FROM post WHERE id = $id");
if($r_26 = $db->query($q_13));
if($r_26->num_rows==1)
{
$stem = $r_26->fetch_object();
$votes[0] = $stem->votes_up;
$votes[1] = $stem->votes_down;
}
return $votes;
}
function getEffectiveVotes(mysqli $db, $id)
{
$votes = getAllVotes($db, $id);
$effectiveVote = $votes[0] - $votes[1];
return $effectiveVote;
}
$id = $_POST['id'];
$action = $_POST['action'];
//current votes
$cur_votes = getAllVotes($db, $id);
//update votes
if($action=='vote_up')
{
$votes_up = $cur_votes[0]+1;
$q_13 = "UPDATE post SET votes_up = $votes_up WHERE id = $id";
$q_13 = "INSERT INTO vote WHERE user = '$username', cID = '$id'";
}
elseif($action=='vote_down')
{
$votes_down = $cur_votes[1]+1;
$q_13 = "UPDATE post SET votes_down = $votes_down WHERE id = $id";
$q_13 = "INSERT INTO vote WHERE user = '$username', cID = '$id'";
}
$r_26 = $db->query($q_13);
if($r_26)
{
$effectiveVote = getEffectiveVotes($db, $id);
echo $effectiveVote." Archers";
}
elseif(!$r_26)
{
echo "Failed to vote!";
}
?>