The tragic star's former partner Mimi O'Donnell was seen arriving on Tuesday at New York's Frank E Campbell funeral home to plan the service. She was accompanied by British assistant Isabella Wing-Davey.
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The outing marked the first time Mimi – the mother of Philip's three children – has been seen in public since the actor's death.
On Wednesday night, hundreds of fans and friends took part in a candlelit vigil outside his New York theatre company.
Father Jim Martin, a Jesuit priest and member of the company, led a community prayer at the ceremony at the Labyrinth Theater Company.
"We come together in a period of terrible mourning and incredible loss, and a period of overwhelming grief and sadness, but also to celebrate a remarkable life," he said.
"We will remember Phil in our own ways. We will remember how he touched our hearts."
A candlelit vigil took place on Wednesday evening outside the late actor's New York theatre company
According to sources, there will be a further gathering of family and friends will gather at the Upper East Side funeral home for a private wake on Thursday from 5pm-9pm.
This will be followed by a funeral on Friday at the 116-year-old St Ignatius of Loyola Catholic Church, which was also the venue for the 1994 service for Jackie Onassis.
Among those expected to attend are Philip's playwright friend David Bar Katz, the man who found Philip at his Greenwich Village apartment after he died of a suspected overdose.
Mr Bar Katz has launched a $50million lawsuit against the National Enquirer's publisher after they printed an article claiming they had an exclusive interview with the playwright in which he confirmed he was in a relationship with the late actor.
Philip's playwright friend Bar David Katz, who has filed a lawsuit against the National Enquirer
"The story is a complete fabrication. There was no interview," the writer's lawyers stated in the complaint, filed in New York's Supreme Court.
They added that their client "never saw Hoffman use heroin or cocaine".
Police investigating Philip's death came across up to 50 envelopes in the actor's home, containing what they believed was heroin, CNN reports. Authorities also found several empty bags which were believed to have contained the class A drug along with prescription drugs, used syringes and other bags containing white powder.
The New York medical examiner's office is conducting an autopsy on Monday to determine Philip's death. Results could take several weeks to come through.