Description:
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I have a problem like this. For a given date I need to get the last day of the previous month. 

For example 
today is 2019-07-31, I needed date is 2019-06-30 



Test script:
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echo date('Y-m-t', strtotime("2019-07-31" . '-1 months'));
echo date("Y-m-d", strtotime("-1 Month"));

Expected result:
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2019-07-31
2019-07-01

Actual result:
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2019-06-30
2019-06-01 or 2019-06-30