PHP实现的连贯操作、链式操作实例

PHP中的连贯操作看起来的确很酷，也非常的方便代码的阅读，当然了必须是在OOP中用才行，在过程化的程序中，就没有必要用这种方法了。有实现这个方法的有用_CALL来实现的，下面的这个例子，则不是用_call的

/*
 * SQL语句组合实例类，始发文章web开发笔记
 * 学习用，非专业类
 * */
class sql{
    private $sql=array("from"=>"",
            "where"=>"",
            "order"=>"",
            "limit"=>"");
  
    public function from($tableName) {
        $this->sql["from"]="FROM ".$tableName;
        return $this;
    }
  
    public function where($_where='1=1') {
        $this->sql["where"]="WHERE ".$_where;
        return $this;
    }
  
    public function order($_order='id DESC') {
        $this->sql["order"]="ORDER BY ".$_order;
        return $this;
    }
  
    public function limit($_limit='30') {
        $this->sql["limit"]="LIMIT 0,".$_limit;
        return $this;
    }
    public function select($_select='*') {
        return "SELECT ".$_select." ".(implode(" ",$this->sql));
    }
}
  
$sql =new sql();
  
echo $sql->from("testTable")->where("id=1")->order("id DESC")->limit(10)->select();
//输出 SELECT * FROM testTable WHERE id=1 ORDER BY id DESC LIMIT 0,10