Can not use POST variable in PHP insert query - php

Question

In my PHP file I do the following
<?php
if(isset($_POST['submit'])){
$con = mysqli_connect(bla);
$query = "insert into users (name,username,password) values($_POST['name'],$_POST['username'],$_POST['password'])";
}
Now, even if if condition is not satisfied, that is when submit is not done, I get error. But when I comment my $query = ... line, there is no error. What is happening?

Answer 1

You need to put '". around your variables, like this:
$query = "insert into users (name,username,password) values('".$_POST['name']."','".$_POST['username']."','".$_POST['password']."')";

Answer 2

place any $_POST['...'] between {}
Like '{$_POST['password']}','...
put this code At the end for display Errors:
if (mysqli_connect_errno()) {
echo mysqli_connect_error();
exit();
}

Answer 3

When you interpolate an array variable into a string, there are two ways to write it: either put curly braces around the variable, or leave out the quotes in the index:
$query = "insert into users (name,username,password)
values('{$_POST['name']}', {'$_POST['username']}', {'$_POST['password']'})";
You also need quotes in the query itself, for correct SQL syntax.

Answer 4

Consider putting your post values into local variables first and then enter the local variables as the values of the insert query. ex:
$name = $_POST['name'];
$query= INSERT INTO users(name)VALUES("$name")