Description:
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PHP document says that SplFileObject->valid() checks if a file pointer is not at EOF, just like SplFileObject->eof().
But since SplFileObject implements Iterator, valid() should not return false while the current element is valid.

Test script:
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$f = new SplFileObject('php://memory', 'r+');
assert('$f instanceof Iterator');
$f->fwrite("line 1");
$f->rewind();
assert('$f->valid() === true');
assert('$f->eof() === false');
assert('$f->current() === "line 1"');
assert('$f->valid() === true'); // fails
assert('$f->eof() === true');