The Insert and Update statements used by PHP beginners construct classes

 
$mysql = new sqlstr("table1"); 
$mysql->set("name","value"); 
$mysql->set("name","1",true); 
echo $mysql->insertSql(); 

 
class sqlstr 
{ 
private $param=array(); 
private $tablename; 
function sqlstr($tablename) 
{ 
$this->tablename = $tablename; 
} 
public function set($name,$value,$isnum=false){ 
$value = str_replace("'","''",$value); 
$this->param[$name]=array($value,$isnum); 
} 
public function insertSql(){ 
$keys=""; 
$values=""; 
foreach($this->param as $key =>$value){ 
$keys = $keys . $key . ","; 
if($value[1]){ 
$values = $values . $value[0] . ","; 
}else{ 
$values = $values . "'" . $value[0] . "',"; 
} 
} 
if($keys!=""){$keys=substr($keys,0,strlen($keys)-1) ;} 
if($values!=""){$values=substr($values,0,strlen($values)-1) ;} 
return "insert into " .$this->tablename ."($keys) values($values)"; 
} 
public function updateSql($cond){ 
$group=""; 
foreach($this->param as $key =>$value){ 
$group .= $key . "="; 
if($value[1]){ 
$group.= $value[0] . ","; 
}else{ 
$group.= "'" . $value[0] . "',"; 
} 
} 
if($group!=""){$group=substr($group,0,strlen($group)-1) ;} 
return "update " . $this->tablename ." set $group where " . $cond; 
} 
}