PHP eldest brother Elder sisters, help younger brother I solve a problem

PHP eldest brother Elder sisters, help me solve a problem
I have a variable: $strDate, the value of this variable may be 2012-01-09 or 2008-05-06 ... Uncertain is any day of all time,
Now I want to return to the month where the value becomes

In other words: Returns the month of the specified date,

When $STRDATE=2012-08-06 is returned: 8
When $STRDATE=2010-02-06 is returned: 2
When $STRDATE=2006-08-06 is returned: 8
When $STRDATE=2015-08-06 is returned: 8

What is this function ';?

------Solution--------------------
echo Date (' n ', Strtotime ($strDate));

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