Description:
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As the summary says, $date->modify('Friday this week') doesn't return a Friday if $date is a Sunday.

Running the script below on 7.0.14 and 7.0.8 yields 2017-01-02, which is a Monday.

However, running the same script on 7.0.5 yields 2017-01-13, a Friday. I expected a Friday.

Test script:
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<?php

$date1 = "2017-01-08"; // this is a Sunday
$date = new \DateTime($date1);
$date->modify('Friday this week');
$dateFormat = $date->format('Y-m-d');
echo $dateFormat;

Expected result:
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Currently, it displays a Monday date on 7.0.14. Testing on 7.0.8 also yields a Monday.

I expect to see a Friday date on both PHP 7.0.5, and 7.0.14.

Here's another link that tests for all php versions and other base days - https://3v4l.org/ZuOhl