LINDSAY LOHAN copped a plea yesterday to charges of reckless driving and lying to police.  And she got a pretty stiff sentence for a change.

--Lindsay will spend 90 days in rehab . . . but it'll be a LOCKDOWN REHAB . . . not one where she can come and go as she pleases or leave early.

--She'll also do 30 days of community service and undergo psychotherapy for 18 months.  She also got two years' probation, and she'll have to submit to drug testing.

--Lindsay also copped to violating her probation for her jewelry theft case and was sentenced to 180 days in jail.  But that sentence was stayed, meaning she won't have to serve it if she stays out of trouble from here on out.

--The hearing was held in Los Angeles, and Lindsay showed up 48 minutes late from New York City after bagging on two commercial flights and finally taking a last-minute private jet.

(--In case you've forgotten, these latest charges against Lindsay stem from that incident last June in which she totaled a Porsche by rear-ending a truck on her way to a movie set.)

(--Lindsay was driving at the time, but she told police her assistant was behind the wheel.  Police also believe Lindsay had an OPEN CONTAINER in the car, and got rid of it after the crash.)

--On her way into the courthouse yesterday, LINDSAY LOHAN was GLITTER-BOMBED . . . which is just an unnecessarily fancy way of saying somebody threw a handful of glitter at her.  She pretty much ignored it.  (--Here's video.)