PHP anti-sql injection class (php pdo prevents sql injection class)

class Model{
protected $tableName="";//Table name
protected $pOb;//pdo class object
function __construct(){
$pdo= new PDO("mysql:host=".DB_HOST.";dbname=".DB_NAME,DB_USERNAME,DB_PASSWORD);
$pdo->exec("set names ".DB_CHARSET);
$this->pOb=$ pdo;
}
/*
* Function: increase
* Parameter: array $arr exp:array('field name'=>value,'field name'=>value,....)
* return: int|false
*/
function add($arr){
//Spell sql statement
$kArr=array_keys($arr);
$kStr=join(",",$kArr);
$vArr=array_values( $arr);
$pStr = '';
foreach ($vArr as $s=>$y){
$vname = "p".$s;
$pStr. =':'.$vname.',';
}
$pStr = substr($pStr,0,-1);
$sql = "insert into {$this-> ;tableName}($kStr) values($pStr)";
print_r($sql);
$pdoS = $this->pOb ->prepare($sql);
 foreach ($vArr as $k=>$y){
$vname = "p".$k;
$$vname = $y;
var_dump($vname,$$vname);
$pdoS -> bindParam(":".$vname, $$vname,PDO::PARAM_STR);
}
$re = $pdoS -> execute();
if($re){ //Added successfully
//Return primary key id value
return $this->pOb->lastInsertId();
}
//Return value
return $re;
}
public function delete($arrWhere){
 if(!empty($arrWhere)){
$strW = " where ";
foreach($arrWhere as $kW=>$vW){
$kn = str_replace(":", "", $kW);
if(count($arrWhere)==1){
$strW .= $kn."=".$kW;
}else{
$strW .= $kn."=".$kW." and " ;
}
}
if(count($arrWhere)>1){
$strW .= " 1=1 ";
}
}
$sql = "delete from {$this->tableName}". $strW;
print_r($sql);
$pdoS = $this->pOb->prepare($sql);
foreach ($arrWhere as $kW=>$vW){
$kn = str_replace( ":", "", $kW);
$$kn = $vW;
if(is_int($vW)){
$pdoS->bindParam($kW,$$kn,PDO::PARAM_INT);
}else if(is_float($vW)){
$pdoS->bindParam($kW,$$kn,PDO::PARAM_INT);
}else{
$pdoS->bindParam($kW,$$ kn,PDO::PARAM_STR);
}
}
$re=$pdoS->execute();
if($re){
 return true;
}else {
return false;
}
}
function update($arrSet,$arrWhere){
//Spell sql statement
$str = "";
$n=0;
foreach ($arrSet as $kS=>$vS){
< ;p>$str .= ",".$kS."=:p".$n++;
}
$str = substr($str, 1);
foreach($arrWhere as $kW=>$vW ){
$kn=str_replace(":","",$kW);
if(count($arrWhere)==1){
$strW .= $kn."=".$kW;
}else {
$strW .= $kn."=".$kW." and ";
}
}
if(count($arrWhere)>1){
$strW .= " 1=1 ";
}
$sql="update {$this->tableName} set {$str} where ".$strW;
//print_r($sql);
< ;p>$pdoS=$this->pOb->prepare($sql);
$x = 0;
foreach($arrSet as $kS=>$vS){
< p>$kS = ":p".$x++;
$$kS = $vS;
if(is_int($vS)){
$pdoS->bindParam($kS ,$$kS,PDO::PARAM_INT);
}else if(is_float($vS)){
$pdoS->bindParam($kS,$$kS,PDO::PARAM_INT);
}else{
$ pdoS->bindParam($kS,$$kS,PDO::PARAM_STR);
}
}

foreach($arrWhere as $kW=>$vW){
$ kn=str_replace(":","",$kW);
$$kn=$vW;//$p0 $p1 $p2
if(is_int($vW)){
$pdoS->bindParam($ kW,$$kn,PDO::PARAM_INT);
}else if(is_float($vW)){
$pdoS->bindParam($kW,$$kn,PDO::PARAM_INT);
}else{
 $pdoS->bindParam($kW,$$kn,PDO::PARAM_STR);
}
}
$re=$pdoS->execute();
if($re){
 return true;< /p>
}else{
return false;
}
}
//Check
function select($field="*",$ArrayWhere="",$ order="",$limit=""){
if(!empty($ArrayWhere)){
$strW = " where ";
foreach($ArrayWhere as $kW=>$vW){
$kn= str_replace(":","",$kW);
if(count($ArrayWhere)==1){
$strW .= $kn."=".$kW;
$strW .= $kn."=".$kW." and ";
}
}
if(count($ArrayWhere)>1){
$strW .= " 1=1 " ;
}
}
if(!empty($order)){
$order="order by ".$order;
}
if(!empty($limit)){
$limit="limit ".$limit;
}
//select 字段列表 from 表名 where 条件 order by 字段 desc|asc limit start,length;
$sql="select {$field} from {$this->tableName} {$strW} {$order} {$limit}";
//print_r($sql);
$pdoS=$this->pOb->prepare($sql);
if(!empty($ArrayWhere)){
foreach($ArrayWhere as $kW=>$vW){
$kn=str_replace(":","",$kW);
$$kn=$vW;
if(is_int($vW)){
$pdoS->bindParam($kW,$$kn,PDO::PARAM_INT);
}else if(is_float($vW)){
$pdoS->bindParam($kW,$$kn,PDO::PARAM_INT);
}else{
$pdoS->bindParam($kW,$$kn,PDO::PARAM_STR);
}
}
}
$re=$pdoS->execute();
if($re){
$pdoS->setFetchMode(PDO::FETCH_ASSOC);
return $pdoS->fetchAll();
}else {
return false;
}
}
}