John 6:6

‘And this he said to test him, for he himself knew what he would do.’

Jesus’ question to Philip was a test. He had been listening to what the disciples had been saying and thus sought to test Philip to see what he would say. This is a quite reasonable assumption. Jesus clearly had a purpose in what He was about to do, for it illustrates the purpose of His coming and reinforces His claim to have come from God. It is not really probable that He would do such a thing on the spur of the moment.