minor #17368 Correct time type return (fullbl)

This PR was submitted for the 6.1 branch but it was merged into the 4.4 branch instead.

Discussion
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Correct time type return

time function returns an int, while DateTime::createFromFormat requires a string!

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Commits
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43e7043 Correct time type return

Author: javiereguiluz

components/phpunit_bridge.rst

@@ -500,7 +500,7 @@ is mocked so it uses the mocked time if no timestamp is specified.
 Other functions with an optional timestamp parameter that defaults to ``time()``
 will still use the system time instead of the mocked time. This means that you
 may need to change some code in your tests. For example, instead of ``new DateTime()``,
-you should use ``DateTime::createFromFormat('U', time())`` to use the mocked
+you should use ``DateTime::createFromFormat('U', (string) time())`` to use the mocked
 ``time()`` function.
 
 To use the ``ClockMock`` class in your test, add the ``@group time-sensitive``