Simple mysql tool implemented in php (execute multiple sql statements)

<?php
header('Content-Type:text/html;charset=GBK');
?>
<form action="" method="post">
<textarea name="sql" cols="90" rows="12"></textarea><br />
<input name="" type="Submit" value="OK!!" />
</form>
<?php
/**
* 简单mysql工具
* 执行多条sql语句
* edit by bbs.it-home.org
*/
if(isset($_GET['sg'])){
 $_SESSION['sg']=$_GET['s'];
}
if(isset($_GET['su'])){
 $_SESSION['su']=$_GET['s'];
}

if(isset($_POST['sql'])){
    $conn = mysql_connect('127.0.0.1', "root", "123qwe");

    if (!$conn) {
        echo "Unable to connect to DB: " . mysql_error();
        exit;
    }

    if (!mysql_select_db("pm")) {
        echo "Unable to select mydbname: " . mysql_error();
        exit;
    }
 if($_SESSION['sg']){
     mysql_query("set names 'gbk'") or die(mysql_error());
 }
 if($_SESSION['su']){
     mysql_query("set names 'utf8'") or die(mysql_error());
 }
 $sql =trim($_POST['sql']);
 
  preg_match_all("/(select|show|update|delete|drop|create|alter|insert)/s+(([`'/"])[^`'/"]+//3|[^;])+;?/i",$sql,$out,PREG_PATTERN_ORDER );
 if(count($out[0])==0) echo "No sql<br/>";

//解决不输入无分号找不到sql的问题
for($i=0;$i<count($out[0]);$i++){
  $sql = $out[0][$i];
  if(substr(strtolower($sql),0,6)=='select'&&strpos($sql,"()")===false&&!preg_match("/limit /d+(,/d+)?$/i",$sql)){
   $sql .= " limit 100";
  }
  echo '$sql='.$sql.'<hr>';
  
  $result = mysql_query(stripslashes($sql));
 
  if (!$result) {
   echo "<font color=#ff0000>Could not successfully run query ($sql) from DB: " . mysql_error()."</font>";   
   continue;
  }
 
  if (mysql_num_rows($result) == 0) {
   echo "No rows found, nothing to print so am exiting";
   continue;
  }
 
  // While a row of data exists, put that row in $row as an associative array
  // Note: If you're expecting just one row, no need to use a loop
  // Note: If you put extract($row); inside the following loop, you'll
  //       then create $userid, $fullname, and $userstatus
  $str = "";
  while ($row = mysql_fetch_assoc($result)) {
   if($str == ""){
    $str = '<tr  bgcolor="#003366" style="color:#ffffff">';
    foreach($row as $k=>$v){
     $str .= "<td>".$k."</td>";
    }
    $str .= "</tr>";
   }
   $str .= "<tr>";
   foreach($row as $k=>$v){
    $str .= "<td>".$v."</td>";
   }
   $str .= "</tr>";
  }
  @mysql_free_result($result);
  echo "<table border=1 >";
  echo $str;
  echo "</table>";
 } 
}
?>