Consider this case:
$yourVar = "a php forum";
$hello = "Unfortunately this is not $yourVar. We are glad to have you here though!";
The result will be - "Unfortunately this is not a php forum. We are glad to have you here though!". In other words, a new data is made out of the two variables - $yourVar interpolates with $hello thus changes it. There are much better examples of variables interpolation in the php manuals, we don't pretend to be experts here :).
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All the best,
the Telerik team
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