Description:
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When running strip_tags on a string containing '<<', the string is truncated at the '<<'.

Reproduce code:
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<?php
$test = "testing << testing testing 1 2 3";
print(strip_tags($test));
?>



Expected result:
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Probably should return the complete string eg:

testing << testing testing 1 2 3

At the worst I would have expected it without the << but certainly containing the rest.

Actual result:
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testing