POST method not inserting data into database table - php

Question

I'm trying to play around with databases and inserting data dynamically with php.
At the moment I have a form with 'post' method and everything seems logical to me but it isn't inserting the data into the table.
Code is attached below, would appreciate if someone could point me into the right direction.
index.php:
<form action="index.php" method="post">
<label for="name">Name</label>
<input type="text" name="name" required>
<label for="breed">Breed</label>
<input type="text" name="breed">
<label for="age">Age</label>
<input type="text" name="age">
<input type="submit" name="submit" value="Submit">
</form>
<?php
require "connect.php";
if('submit') {
$name = $_POST['name'];
$breed = $_POST['breed'];
$age = $_POST['age'];
$newdog = mysqli_query('INSERT INTO `dogs`(`name`, `breed`, `age`) VALUES ([$name],[$breed],[$age)');
if ($newdog) {
echo "$name has been added to the database";
} else {
echo "$name has not been added to database.";
};
};
?>
connect.php:
<?php
$connect = mysqli_connect('localhost', 'max', 'password', 'db_test');
?>

Answer 1

<?php
require "connect.php";
if(isset($_POST['submit'])) {
$name = $_POST['name'];
$breed = $_POST['breed'];
$age = $_POST['age'];
$newdog = mysqli_query($connect, 'INSERT INTO dogs(name, breed, age) VALUES ("'.$name.'","'.$breed.'","'.$age.'")');
if ($newdog) {
echo "$name has been added to the database";
} else {
echo "$name has not been added to database.";
};
};
?>

Answer 2

Change if('submit') {
TO
if(isset($_POST['submit'])){//check if it is set
}
Also change this line:
$newdog = mysqli_query('INSERT INTOdogs(name,breed,age) VALUES ([$name],[$breed],[$age)');
TO
$newdog = mysqli_query($connect, 'INSERT INTOdogs(name,breed,age) VALUES ($name,$breed,$age)');//remove square bracktes and add connection variable
Your code is very well vulnerable to SQL injection
Using prepared statements,
$stmt = $connect->prepare("INSERT INTO dogs (`name`, `breed`, `age`) VALUES (?, ?, ?)");
$stmt->bind_param("sss", $name, $breed, $age);
if($stmt->execute() == true){
echo 'Saved';
} else {
echo 'Error '. $stmt->error;
}

Answer 3

Own answer: Figured it out, I had to configure PHPStorm to use MAMP Apache server instead of the internal server since that one apparently doesn't like $_POST[] requests