src/Mysqli.php
public function field($field = '*')
    {
        if (!$field) {
            $this->field = '*';
            return $this;
        }

        $newField = '';
        $field    = is_array($field) ? $field : explode(',', $field);
        foreach ($field as $k => $v) {
            if (stripos($v, 'as') === false && stripos($v, '*') === false && stripos($v, '`') === false && stripos($v, '.') === false && stripos($v, 'concat') === false) {
                $newField .= '`' . $v . '`,';
            } else {
                $newField .= $v . ',';
            }

        }

        $newField = substr($newField, 0, -1);

        $this->field = $newField;

        $this->build['field'] = $field;

        return $this;
    }
public function field($field = '*')
    {
        if (!$field) {
            $this->field = '*';
            return $this;
        }

        $newField = '';
        $field    = is_array($field) ? $field : explode(',', $field);
        foreach ($field as $k => $v) {
            if (stripos($v, 'as') === false && stripos($v, '*') === false && stripos($v, '`') === false && stripos($v, '.') === false && stripos($v, 'concat') === false) {
                $newField .= '`' . $v . '`,';
            } else {
                $newField .= $v . ',';
            }

        }

        $newField = substr($newField, 0, -1);

        $this->field = $newField;

        $this->build['field'] = $field;

        return $this;
    }
查询字段
@date   2017-03-19T16:18:09+0800
@author ChenMingjiang
@param  [type]                   $field [description]
@return [type]                          [description]