Invalid usage of class constant fetch expression PHP-W1006
Bug risk
Critical
10 months ago
—
2 years old
No results found
That’s all we can say right now.
Description
The class constant you're trying to access isn't valid and could lead to runtime errors.
This issue is raised for the following cases:
- Trying to access a class that doesn't exist.
- Using
self/static/parentoutside a class. - Trying to access a class constant defined in a class that is not in scope.
- Accessing a private/undefined constant in a class.
- Trying to access the
::classconstant on a dynamic string. - Using the
::classconstant on an expression in PHP < 8.0. Accessing this value on an expression is supported only in PHP 8.0 and later.
Any of the operations mentioned above would result in a fatal runtime error, and may potentially crash the application. Avoid performing such operations.
Bad practice
class Version
{
private const PHP_74 = 70400;
public const PHP_80 = 80000;
}
echo PhpVersion::PHP_80; // invalid: class "PhpVersion" doesn't exist
echo self::PHP_74; // invalid: cannot use "self" outside of a class
echo Version::PHP_56; // invalid: class constant "PHP_56" is undefined
$version = new Version;
echo $version::class; // note: this will only work on PHP 8.0 or later
Recommended
class Version
{
public const PHP_56 = 50600;
public const PHP_74 = 70400;
public const PHP_80 = 80000;
}
// valid: make sure class exists and constant is defined
echo Version::PHP_80;
// valid: make sure to define constant that is being accessed
echo Version::PHP_56;
// valid: change visibility to public, or implement a getter method to retrieve the private constant or properties
echo Version::PHP_74;