Building MySQL query with need for variable operators PHP PDO - php

Question

Is there any standard or best way in PHP PDO database class to change the operator from "=" to "IS" when I don't know if the value I'm going to pass is NULL or not. Here is an example of what I mean.
I have two variables. I want a count of the results that match. Sometimes one or both of the variables can be NULL. But MySQL requires a different operator to find NULL (IS NULL).
I'm currently just creating another variable for the operator and when I build the query I inject it in as so:
// First create a variable "=" or "is" depending on whether var1 and var2 are NULL or not
if($var1 == NULL) $var1_operator = "IS";
else $var1_operator = "=";
if($var2 == NULL) $var2_operator = "IS";
else $var2_operator = "=";
// Build the query
$query = 'SELECT count(*) as count FROM table
WHERE var1 '.$var1_operator.' :var1 AND var2 '.$var2_operator.' :var2';
// Conduct the query
$prepare = $db_connection->prepare($query);
$prepare->bindValue(':var1', $var1, PDO::PARAM_STR);
$prepare->bindValue(':var2', $var2, PDO::PARAM_STR);
$prepare->execute();
$results = $prepare->fetch();
Is there another way to do this? This works to bindValue using PARAM_STR even when the value is NULL and not really a string. The query returns the correct value count. Just not sure if there is better practice for doing it.

Answer 1

As you are using mysql, you can use its spaceship operator, <=>:
$query = 'SELECT count(*) FROM table WHERE var1 <=> ? AND var2 <=> ?';
$prepare = $db_connection->prepare($query);
$prepare->execute([$var1, $var2]);
$count = $prepare->fetchColumn();
But in general, if you need variable operators or other query parts, such a conditional query building is the only way.
A more generalized solution can be found in my article How to create a WHERE clause for PDO dynamically:
// always initialize a variable before use!
$conditions = [];
$parameters = [];
// conditional statements
if (!empty($_GET['name']))
{
// here we are using LIKE with wildcard search
// use it ONLY if really need it
$conditions[] = 'name LIKE ?';
$parameters[] = '%'.$_GET['name']."%";
}
if (!empty($_GET['sex']))
{
// here we are using equality
$conditions[] = 'sex = ?';
$parameters[] = $_GET['sex'];
}
if (!empty($_GET['car']))
{
// here we are using not equality
$conditions[] = 'car != ?';
$parameters[] = $_GET['car'];
}
// the main query
$sql = "SELECT * FROM users";
// a smart code to add all conditions, if any
if ($conditions)
{
$sql .= " WHERE ".implode(" AND ", $conditions);
}
// the usual prepare/execute/fetch routine
$stmt = $pdo->prepare($sql);
$stmt->execute($parameters);
$data = $stmt->fetchAll();
so in these conditions above whatever logic could be implemented, including operator change or anything.