MAMP can't establish database connection - php

Question

I'm trying to save data from a multi-page form into a database. I followed this tutorial but the connection always fails. I had to change to function from mysql_connect to mysqli_connect as I am running PHP7, so this could be part of the issue. Here is the code:
<?php
session_start();
if (isset($_POST['state'])) {
if (!empty($_SESSION['post'])){
if (empty($_POST['address1'])
|| empty($_POST['city'])
|| empty($_POST['pin'])
|| empty($_POST['state'])){
// Setting error for page 3.
$_SESSION['error_page3'] = "Mandatory field(s) are missing, Please fill it again";
header("location: finder-step-3.php"); // Redirecting to third page.
} else {
foreach ($_POST as $key => $value) {
$_SESSION['post'][$key] = $value;
}
extract($_SESSION['post']); // Function to extract array.
$connection = mysqli_connect("localhost", "root", "root");
$db = mysqli_select_db($connection, "finder_form"); // Storing values in database.
$query = mysqli_query($db, "insert into detail (name,email,contact,password,religion,nationality,gender,qualification,experience,address1,address2,city,pin,state) values('$name','$email','$contact','$password','$religion','$nationality','$gender','$qualification','$experience','$address1','$address2','$city','$pin','$state')", $connection);
if ($query) {
echo '<p><span id="success">Form Submitted successfully..!!</span></p>';
} else {
echo '<p><span>Form Submission Failed..!!</span></p>';
}
unset($_SESSION['post']); // Destroying session.
}
} else {
header("location: finder-step-1.php"); // Redirecting to first page.
}
} else {
header("location: finder-step-1.php"); // Redirecting to first page.
}
?>
Can anyone spot where I am going wrong? Thanks in advance!
Update 1:
#Damon Swayn, I have changed it to the below but still receive the form submission failed message:
$connection = mysqli_connect("localhost", "root", "root", "finder_form");
$query = mysqli_query($connection, "insert into detail (name,email,contact,password,religion,nationality,gender,qualification,experience,address1,address2,city,pin,state) values('$name','$email','$contact','$password','$religion','$nationality','$gender','$qualification','$experience','$address1','$address2','$city','$pin','$state')", $connection);
if ($query) {
echo '<p><span id="success">Form Submitted successfully..!!</span></p>';
} else {
echo '<p><span>Form Submission Failed..!!</span></p>';
}
#lps, I setup the following on a test.php page in the same directory and it connected successfully:
<?php
$con = mysqli_connect('localhost', 'root', 'root') or die('Could not connect the database : Username or password incorrect');
mysqli_select_db($con, 'finder_form') or die ('No database found');
echo 'Database Connected successfully';
?>
Update 2: Solved
The changes suggested by Damon Swayn worked, I just had to remove the $connection at the end of the query. Here is the working code:
$connection = mysqli_connect("localhost", "root", "root", "finder_form");
$query = mysqli_query($connection, "insert into detail (name,email,contact,password,religion,nationality,gender,qualification,experience,address1,address2,city,pin,state) values('$name','$email','$contact','$password','$religion','$nationality','$gender','$qualification','$experience','$address1','$address2','$city','$pin','$state')");
if ($query) {
echo '<p><span id="success">Form Submitted successfully..!!</span></p>';
} else {
echo '<p><span>Form Submission Failed..!!</span></p>';
}

Answer 1

mysqli_connect() can take 4 parameters, the fourth being the database name.
you are using the return value of mysqli_select_db() as the connection param for every following call, mysqli_select_db() returns a boolean true/false value, try replacing the $db param in the following calls after mysqli_select_db() with the $connection variable.