open ext/standard/html.c

find:
    /* Default is now UTF-8 */
    if (charset_hint == NULL)
        return cs_utf_8;

    if ((len = strlen(charset_hint)) != 0) {
        goto det_charset;
    }

    zenc = zend_multibyte_get_internal_encoding(TSRMLS_C);
    if (zenc != NULL) {...}

    charset_hint = SG(default_charset);
    if (charset_hint != NULL && (len=strlen(charset_hint)) != 0) {
        goto det_charset;
    }

replace to:
    if ((len = strlen(charset_hint)) != 0) {
        goto det_charset;
    }

    charset_hint = SG(default_charset);
    if (charset_hint != NULL && (len=strlen(charset_hint)) != 0) {
        if(charset_hint == "utf-8"
            || charset_hint == "UTF-8")
                return cs_utf_8;
        goto det_charset;
    }

    /* Default is now UTF-8 */
    if (charset_hint == NULL)
        return cs_utf_8;

    zenc = zend_multibyte_get_internal_encoding(TSRMLS_C);
    if (zenc != NULL) {...}