Find the Segment code: Determine whether there is duplicate content in the array, if there is only the specified number of updates, no add

Find the Segment code: Determine whether there is duplicate content in the array, if there is only the specified number of updates, no add
Content:

First Grade x 2, sophomore x 10, third grade X 5 ...

Determine if there is a second grade, if there is a 5 result: first grade x 2, sophomore x 15, third grade X 5 ...
------Solution--------------------

$QQ = "First grade x 2, second year X 10, third grade X 5";
$k = ' second grade ';
echo Preg_replace ("/(? <= $k X) \d+/e", ' $5 ', $QQ);

First Grade x 2, sophomore x 15, third grade X 5

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