Inserting an array into a relational table - php

Question

I have 3 tables:
user_login
doc_list
user_cat_link_table
So I am creating a new user and apart of the form shows an array of the available categories which are pulled from the cat_list table.
I am struggling to along with the other form data update the user_cat_link_table.
The script to take the ID of the new user and take the ID of the category selected from the checkboxes array:
Here is my input form:
<form action="actions/add_emp.php" method="post">
<input type="text" name="user" placeholder="Username" required="required" /><br/>
<input type="text" name="pass" type="password" placeholder="Password"/></label><br/>
<input type="text" name="firstname" id="name" required="required"
placeholder="Firstname"/><br />
<input type="text" name="lastname" id="email" required="required"
placeholder="Lastname"/><br/>
<input type="email" name="email" id="city" required="required"
placeholder="Email Address"/><br/>
<input type="text" name="extension" id="extension" required="required"
placeholder="Extension Number"/><br/>
<select name="title">
<option selected disabled>Please Select a Job Title...</option>
<option disabled></option>
<option disabled>Helpesk:</option>
<option value="Technical Support Advisor">Technical Support Advisor</option>
<option value="Deputy Team Leade">Deputy Team Leader</option>
<option value="Team Leader">Team Leader</option>
<option value="Incident Resolution Advisor">Incident Resolution Advisor
</option>
<option disabled></option>
<option disabled>Call Centre:</option>
<option value="Technical Support Advisor">Technical Support Advisor</option>
<option value="">Deputy Team Leader</option>
<option value="">Team Leader</option>
<option disabled></option>
</select>
<div id="checkboxlist" >
<?php
foreach($category as $cat){
?>
<input type="checkbox" value="<?php echo $cat["cat_id"]; ?>"
name="cat_no[]" id="box1"> <?php echo $cat["cat_title"]; ?></a><br>
<?php
}
?>
</div>
<input type="submit" value="Add User" name="submit"/><br />
</form>
I can see if I do a print_r() or var_dump() I am getting the results I expect:
Array ( [action] => id
[user] => test23wer3e4weret4essd
[pass] => test [firstname] => test
[lastname] => test
[email] => tes#test.com
[extension] => 1234
[cat_no] => Array ( [0] => 69
[1] => 70
[2] => 71 )
[submit] => Add User )
Here is the form which acts as the script to insert the data into both the user_login table (which works) but its the part at the bottom trying to insert into the join table I am having trouble with:
<?
session_start();
session_regenerate_id();
if(!ini_get('date.timezone'))
{
date_default_timezone_set('GMT');
}
if(isset($_POST["action"])){
if(isset($_POST['submit'])){
include_once'../../config.php';
$dbh = new PDO("mysql:host=$hostname;dbname=dashboardr",$username,$password);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if(isset($_POST['user']) && isset($_POST['pass'])){
$password=$_POST['pass'];
$sql=$dbh->prepare("SELECT COUNT(*) FROM `user_login` WHERE `username`=?");
$sql->execute(array($_POST['user']));
if($sql->fetchColumn()!=0){
die("User Exists");
}else{
function rand_string($length) {
$str="";
$chars = "subinsblogabcdefghijklmanopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
$size = strlen($chars);
for($i = 0;$i < $length;$i++) {
$str .= $chars[rand(0,$size-1)];
}
return $str;
}
$p_salt = rand_string(20);
$site_salt="subinsblogsalt";
$salted_hash = hash('sha256', $password.$site_salt.$p_salt);
$sql=$dbh->prepare("INSERT INTO `user_login`
(`id`, `username`, `password`, `psalt`,
`firstname`, `lastname`, `email`, `extension`)
VALUES (NULL, ?, ?, ?, ?, ?, ?, ?)");
$sql->execute(
array($_POST['user'], $salted_hash, $p_salt, $_POST["firstname"],
$_POST["lastname"], $_POST["email"], $_POST["extension"]));
print_r($_POST);
die();
$docId = $dbh->lastInsertId();
$sql = "INSERT INTO `user_cat_link_table`(`UserID`, `Cat_ID`) VALUES";
$values = "";
$params = [];
foreach($_POST["cat_no"] as $cat)
{
$values.= "(?, ?), ";
$params[] = $cat; // correct here
$params[] = $docId;
}
$values = substr($values, 0, -2);
$sql.= $values;
$query = $dbh->prepare($sql);
$query->execute($params);
if ($dbh->query($sql)) {
}else{}
$dbh = null;
} //catch(PDOException $e)
header ('Location: ../list_doc.php?success=1');
}
}
}
?>