Description:
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Hello, since i am not a pro and i haven't submited a bug before, but i think there is a bug with FILTER_SANITIZE_STRING.

All chars are being cutter after < char in the string.

You can check my test script which is pretty simple.

I am sorry if it is my bad and I am doing something worng :(

Test script:
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$query = ' this is ok so far < but this part here will be missing';

echo "<pre>";
print_r(filter_var ($query, FILTER_SANITIZE_STRING));
echo "</pre>";

Expected result:
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this is ok so far &lt; but this part here will be missing

Actual result:
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this is ok so far