How does PHP obtain the returned string from the COM component?

How does PHP obtain the returned string from the COM component? The COM component defines a method HRESULTGetStr ([in, out] BSTR * vStr, [in, out] LONG * vLen, [out, retval] LONG * vError). The method is implemented as follows: CC ++ codeSTDMETHODIMPMC_MyClass: GetStr (BSTR * vStr, how does PHP obtain the returned string from the COM component?
Define a method in the COM component
HRESULT GetStr ([in, out] BSTR * vStr, [in, out] LONG * vLen, [out, retval] LONG * vError );

Method implementation:

C/C ++ code

  STDMETHODIMP MC_MyClass::GetStr(BSTR* vStr, LONG* vLen, LONG* vError){    *vError = 0;    if(0 == vStr)    return S_FALSE;    if(0 == vLen)    return S_FALSE;    wchar_t tStr[] = L"This is a string from com!";    memcpy(*vStr, tStr, wcslen(tStr));    *vLen = wcslen(tStr);    *vError = 1;    return S_OK;}

PHP calls this method

C/C ++ code

  $tStr = "";$tLen = 100;$tStr = str_pad($tStr, $tLen, "0");$tRes = $tCom->GetStr(&$tStr, &$tLen);

Result
$ TRes = 1;
$ TStr = "";
$ TLen = 26;

Solution: Why is $ tStr empty?

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It may be retrieved using the vsscanf function.
Unable to provide further suggestions because there are no test conditions
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Memcpy (* vStr, tStr, wcslen (tStr ));

Wcslen is the number of UNICODE characters, memcpy is the number of copied bytes, it is obvious that wcslen (tStr) * 2, and not * vStr, directly vStr.
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Discussion

Memcpy (* vStr, tStr, wcslen (tStr ));

Wcslen is the number of UNICODE characters, memcpy is the number of copied bytes, it is obvious that wcslen (tStr) * 2, and not * vStr, directly vStr.