Why urine test for pcp was positive yesterday and negative today?

A urine test for PCP (phencyclidine) can yield different results due to various factors, such as the sensitivity of the test, timing of the drug use, and individual metabolism. PCP can be detected in urine for several days after use, but if the test was conducted at different times or if the urine was diluted, the results might vary. Additionally, false positives or negatives can occur depending on the specific assay used. It's also possible that the individual did not use PCP again after the initial positive test.