Description:
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Hey. I encountered a weird inconsistency in foreach() behavior over plain arrays. See the code below. In certain specific cases loop will skip second iteration with no apparent reason.

It reproduces (at least) on 7.2.7-7.2.9 on both windows and linux, but NOT on 7.1.21 or below.

Test script:
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$arr = [1 => 1, 3 => 3];           // [1 => 1, 2 => 3] will print both keys
foreach($arr as $key => &$val) {   // without & will print both keys
    echo "See key {$key}\n";
    $arr[0] = 0;                   // without this line will print both keys
    unset($arr[0]);
}


Expected result:
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See key 1
See key 3


Actual result:
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See key 1