Class PHPStan\Reflection\PassedByReference

Describes how a function/method parameter is passed: by value or by reference.

Three modes:

• No: Passed by value — the argument expression is evaluated and its value is copied.
• ReadsArgument: Passed by reference, but the function reads the existing variable. The variable must already exist. Example: sort(&$array).
• CreatesNewVariable: Passed by reference, and the function may create the variable if it doesn't exist. Example: preg_match($pattern, $subject, &$matches) where $matches doesn't need to be defined beforehand.

This distinction matters for PHPStan's scope analysis — when a function takes a parameter by reference with "creates new variable" semantics, PHPStan knows the variable will exist after the call even if it wasn't defined before.

Used as the return type of ParameterReflection::passedByReference().