Questions about the Select dropdown box in PHP

Problems with the Select dropdown box in PHP
This is a modify page drop-down box Please select Finance Department Office Product Development Dept. Application Development Department
I want to open the Modify page every time the default is the value read from the database $project_department, but now each time is displayed "please select"
Ask the gods how to write? I wrote one down here, but it didn't work.

------Solution--------------------
Add id= ' project_department ' to your Select box


So try, in fact, the output should be controlled.
------Solution--------------------
2 floor of the can, if not the problem to put it back to only one display of the problem, it is best to look at the code and then rewrite it again sometimes this problem occurs

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