/*
 * 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