8:00 PM PT -- Conor posted bail and strolled out of the Miami-Dade County Jail a little while ago. He was totally reserved as someone escorted him to a waiting SUV.

No billionaire strut tonight.

5:16 PM PT -- Conor's attorneys just released a statement on the arrest.

"Last evening Conor McGregor was involved a minor altercation over a cell phone that resulted in a call to law enforcement. Mr. McGregor appreciates the response of law enforcement and pledges his full cooperation."

Conor McGregor has been arrested again ... this time for allegedly smashing the phone of a fan outside the Fontainebleau hotel in Miami Beach.

According to the police report, obtained by TMZ Sports, at around 5 AM Monday, the owner of the phone was walking out of the hotel at the same time as Conor and as the fan attempted to take a photo, Conor slapped the victim's phone out of his hand, causing it to fall to the ground. McGregor then allegedly stomped on the phone several times, damaging it.

According to cops, McGregor then picked up the phone and walked away with it.

It appears the incident was captured on surveillance video.

He's been booked for robbery/strong-arm and criminal mischief over $1,000. He is currently being held on $12,500 bail.

It's unclear why Conor was outside the hotel at 5 AM, but it seems he and the fan were leaving LIV nightclub, which is inside the hotel. LIV closes at 5 AM.

It appears Conor went back to the Miami home where he was staying. The alleged victim subsequently filed a police report. Cops went to Conor's home and arrested him just before 6 PM ET.

He's been in South Florida over the last few days with his girlfriend, Dee Devlin, and their son, Conor Jr., along with other family members. Conor and his family were in Miami to celebrate his mother's birthday. He had rented out the Versace Mansion for the blowout.

The timing of the new arrest is interesting ... TMZ Sports broke the story Conor just completed his sentence in the dolly attack case. He completed 5 days of community service at churches in Brooklyn as well as completing an anger management class.

If Conor is convicted in the phone smashing case, the Florida can take Conor's previous transgressions into consideration during sentencing.