How to execute SQL query stored in variable in PHP

How to execute SQL query stored in variable in PHP

I'm trying to run a query in PHP using mysqli_query()
My query is stored in variable $query as follows:
$query = "INSERT INTO spaces (";
$keys = '';
$values = '';
foreach ($newrow as $key=>$value){
$keys .= $key.",";
$values .= "'".$value."',";
}
$keys = substr($keys, 0, -1);
$values = substr($values, 0, -1);
$query .= $keys;
$query .= ") values(";
$query .= $values;
$query .= ")";`
On using echo $query, it shows the generated query.
However, I must now execute this query in the database.
Currently, I'm using $result = mysqli_query($success, $query); where
$result is the variable for establishing connection to database. However,
this isn't working and neither is $result = mysqli_query($query);
I need help in figuring out how to correctly pass a variable as query.