NOT COOL! Philip Seymour Hoffman who infamously played a rock critic/drug addict in “Almost Famous” admits heroin addiction.

Hoffman,  45, has completed a 10-day rehab program to fight a heroin addiction, RadarOnline reported.

Philip had kicked the habit 23 years ago, but started messing with drugs again last year, it’s been revealed.

 His problems reportedly began by abusing prescription pills before he began snorting “H,” heroin, up his nose.

Hoffman had been active in the sober community for years, aiding other struggling stars overcome her addictions.

“Philip has always been a role model in recovery,” a source said. “His story inspired thousands of people over the years and he never thought he was too good or too famous to help people.”

The Academy Award winner for Capote  is said to have realized that he had a problem after abusing heroin for nearly a week.

He promptly went to rehab for 10 days and reportedly checked himself out May 24.

POP FYI: Lester Bangs, who Hoffman played in the now-classic “Almost Famous”, died in New York City on April 30, 1982, of an overdose of Darvon, Valium and cough syrup Nyquil.