I have a db table named 'people' with the primary key userId that is generated with autoincrement. The table has a column dateTimeCreation (a mysql DATETIME type) whose value is set in the php script using

$dateTimeCreation = date ( 'Y-m-d h:m:s' );

and inserted in the record creation query along with several other values.
To get the userId of the new record immediately after creation i execute a query

"SELECT userId from people where dateTimeCreation = STR_TO_DATE('{$dateTimeCreation}', '%Y-%m-%d %h:%i:%s');";

Unexpectedly the query sometimes returns records with dateTimeCreation values that arent perfect matches. It has returned records with year/month/date and hour matching and minute and second not matching, this when a record with perfectly matching dateTimeCreation value existed lower in the table (lower as seen in phpmyadmin gui).
This is one of the nasty problems that occur only sometimes. But i checked my logs and incorrect matches were definitely retreived.
I am aware that there are better techniques to get the new records as they are created, but some parts of my code still depend on queries using dateTimeCreation so i have to make this comparison work.
Any suggestions?