Passing booleans to a method can be code smell, as it is not clear what a boolean does by reading the calling code.

$this->getPrice(true);

A common way to improve on this is by assigning the boolean to a variable with a descriptive name.

$this->getPrice($includingTaxes = true);

Instead of using a temporary variable, you could also use PHP 8's named arguments.

$this->getPrice(includingTaxes: true);

A an even better way to solve this would be to introduce methods with a descriptive name.

class Invoice
{
    public function getPriceIncludingTax(): int
    {
        // …
    }
    
    public function getPriceExcludingTax(): int
    {
        // …
    }
}

// …


$invoice->getPriceIncludingTax();

In general, don't avoid using longer names when they clarify your code. Quality code is not about writing the least amount of words and letters, it's about writing code that can be understood and maintained for years to come.

If you want to read more tips like this one, consider picking up our course on Writing Readable PHP.