Arithmetic operation with unsupported operands

Reports arithmetic and bitwise expressions with unsupported operands.

Starting with PHP 8.0, using the arithmetic and bitwise operators +, -, *, /, **, %, <<, >>, &, |, ^, ~, ++, -- when one of the operands is an array, resource, or non-overloaded object will result in a TypeError. The only exception is the array + array merge operation, which remains supported.

See PHP's internal test source for the complete list of operations.