php insert to sql not working - php

Question

I'm on ubuntu running on apache2.
<?php
$con = mysqli_connect("localhost", "root", "password", "loops");
if (!mysqli_connect_errno()) {
echo "Error to connect: ".mysqli_connect_error();
}
$firstName = $_POST['firstname'];
$lastName = $_POST['lastname'];
$age = $_POST['age'];
echo "First: ".$firstName."<br />Age: ".$age;
$sql = "INSERT INTO persons (FirstName, LastName, Age)
values (".$firstName.",".$lastName.",".$age.")";
if (!mysqli_query($con)) {
die("Error :".mysqli_error($con);
}
echo "1 added";
mysqli_close($con);
?>
I don't know what to do now, but the error seems to be on the '$sql', 'cause when I put that
under a comment, the rest works...

Answer 1

You forgot the infamous mistake of wrapping the varchar variables with single quote '
"INSERT INTO persons (FirstName, LastName, Age)
values ('".$firstName."','".$lastName."','".$age."')";
Additionally, It's highly risky for you, not be using protections against SQL Injections

Answer 2

Try this, mysqli_query($con, $sql) You need to execute the query so that it will store into the database
$sql = "INSERT INTO persons (FirstName, LastName, Age)
values ('".$firstName."','".$lastName."','".$age."')";
if (!mysqli_query($con, $sql)) {
...................^
die("Error :".mysqli_error($con);
}

Answer 3

Try this:
$sql = "INSERT INTO persons (`FirstName`, `LastName`, `Age`) values (".$firstName.",".$lastName.",".$age.")";
If this doesn't work, what error do you get.