How to get the matrix form of a quantum circuit in qiskit?

After I create a quantum circuit in qiskit, I want to output its matrix form. Any idea how to do it?

Qiskit now support the matrix representation of a circuit:

from qiskit.quantum_info import Operator

U = Operator(circ)

# Show the matrix form results
U.data

see also

qiskit.org/documentation/tutorials/circuits/01_circuit_basics.html#Unitary-representation-of-a-circuit