Description:
------------
PHP's strpbrk() passes its string arguments directly to libc strpbrk(), which
considers NUL byte a string-terminatig character rather than a normal part of
the string.

note that, in the test script below, the strpbrk() matches neither the NUL byte,
nor the `a' character (because it occurs after a NUL byte in $haystack), nor
even the `b' character (because it occurs after a NUL byte in $char_list).

Test script:
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$haystack = "foob\x00ar";
$char_list = "a\x00b";
$v = strpbrk($haystack, $char_list);

Expected result:
----------------
$v === "b\x00ar"

Actual result:
--------------
$v === FALSE