Description:
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When run on Windows (WAMP) with Apache (using PHP alone in a console is fine), the function disk_total_space() throws Warning: disk_total_space(): The system cannot find the path specified. if a relative path is supplied.

Test script:
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<?php
echo getcwd() . DIRECTORY_SEPARATOR . 'test' . PHP_EOL;
echo realpath('test') . PHP_EOL;

echo disk_total_space(getcwd() . DIRECTORY_SEPARATOR . 'test') . PHP_EOL;
echo disk_total_space(realpath('test')) . PHP_EOL;
echo disk_total_space('test') . PHP_EOL; // fails