Passing string and variable to php function - php

Question

I have a script that manage my tables and contains function to get list or to get certain data by id.
Right now one of my functions looks like this
//Returns a Series Object matching the given series id
public static function getById( $WHERE, $id ){
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$sql = "SELECT * FROM series $WHERE $id";
$st = $conn->prepare( $sql );
$st->execute();
$row = $st->fetch();
$conn = null;
if( $row ) return new Series( $row );
}
But I want it to be like this
//Returns a Series Object matching the given series id
public static function getById( $statement ){
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$sql = "SELECT * FROM series $statement";
$st = $conn->prepare( $sql );
$st->execute();
$row = $st->fetch();
$conn = null;
if( $row ) return new Series( $row );
}
So instead of having to do this
$series = Series::getById( ( string ) "WHERE id=", (int) $_POST['seriesId'] );
I can do this
$series = Series::getById( ( string ) "WHERE id=$_POST['seriesId']" );

Answer 1

The correct way of passing that value to your function would be like below:
$series = Series::getById("WHERE id=".$_POST['seriesId']);