$iTest1 = 2;
$iTest2 = 2;

$iTest3 = 100000000000000;
$iTest4 = 100000000000;

$iTest5 = ( $Test1 $iTest3 ) + ( $iTest2 $iTest4 ) + 1;

echo $iTest1; // is 2
echo "
";
echo "
";
echo $iTest2; // is 2
echo "
";
echo "
";
echo $iTest3; // is in debugger 276447232 but in reality 100000000000000
echo "
";
echo "
";
echo $iTest4; // is in debugger 1215752192 but in reality 100000000000
echo "
";
echo "
";
echo $iTest5; // is in debugger -1310568447 but in reality 200200000000001

I mistakenly posted this bug in the phpstorm-bugtracker:

https://youtrack.jetbrains.com/issue/WI-31398#

Here is some more info and screenshots to this topic.