This guide expressly avoids any requirement regarding the use of $StudlyCase, $camelCase, or $under_score variable and property names. It is often the case that variable names map directly field names in external data sources. Changing between naming conventions when changing contexts merely to suit a style guide would be counterproductive in such cases.
Some projects prefix function and method names with a single underscore to indicate a protected or private visibility. This guide discourages but does not disallow that practice.
Whatever naming convention is used should be applied consistently within a reasonable scope. That scope may be vendor-level, package-level, class-level, or function-level.
Class properties should explicitly note the visibility keyword.
<?php
namespace Vendor\Package;
class ClassName
{
public $property = null;
}
Global variables are disallowed.