PHP实现的连贯操作、链式操作实例

/*
 * 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