PHP错误：Only variables should be passed by reference
原因在于PHP5.3版本开始，array_shift不支持函数返回
$tag_sel = array_shift(explode(' ', $tag));上述写法改成下面写法
$tag_tmp = (explode(' ', $tag));
$tag_sel = array_shift($tag_tmp);
//$tag_sel = array_shift(explode(' ', $tag));
