PHP 7.x SQLITE3 PDO - 是关闭PDO连接的execute（）吗？

Question

I have this code that works weird with SQLITE3 , since the same code with MYSQL works fine

The issue is the line commented with "ISSUE" at line #31, because with MYSQL/MariaDB that "re connection" is NOT needed

Now I better explain

If the IF routine is not entered, I have NO error

If the IF routine is processed, line #34 throws

Uncaught Error: Call to undefined method PDOStatement::prepare()

like if the $PDO-execute(); inside the IF is destroying the PDO istance

You may say, well, no problem, now you have fixed it ... yes, but I'd like to understand why this happen.

Also portability is a point. If this is PDO ... except for the connection, the rest of the script should work and moved among various supported PDO DBs

Thank you if you kindly hint what is the reason and what is it

<?php

// Create or open a database file
$PDO = new PDO('sqlite:myDatabase.sqlite3');


if( isset($_POST['NoteUpdateText'])  && !empty(trim($_POST['NoteUpdateText'])) ){

    //$testo = $_POST['NoteUpdateText'];

    try {

            $PDO = $PDO->prepare('UPDATE ajax SET testo = :testo WHERE id = :id');
            $PDO->bindValue(':testo', $_POST['NoteUpdateText']);
            $PDO->bindValue(':id', 1);
            $PDO->execute();

        // echo a message to say the UPDATE succeeded
        //echo $stmt->rowCount() . " records UPDATED successfully";
        }
    catch(PDOException $e)
        {
        echo $sql . "<br>" . $e->getMessage();
        }
}

// In EVERY case, load the actual DB record and return it to javascript

$PDO = new PDO('sqlite:myDatabase.sqlite3');  // --- ISSUE, theoretically this is already opened at line #3 ---

    try {
            $PDO = $PDO->prepare('SELECT testo FROM ajax WHERE id=1 LIMIT 1'); 
            $PDO->execute(); 
            $row = $PDO->fetch();
            //var_dump($row);
            echo $row["testo"];
        }
    catch(PDOException $e)
        {
        echo $sql . "<br>" . $e->getMessage();
        }       

?>

FIXED CODE

<?php

//include 'db-con2.php';
// table: ajax  
// col: testo

// Create or open a database file
$PDO = new PDO('sqlite:myDatabase.sqlite3');

if( isset($_POST['NoteUpdateText'])  && !empty(trim($_POST['NoteUpdateText'])) ){

    //$testo = $_POST['NoteUpdateText'];

    try {

            $statement = $PDO->prepare('UPDATE ajax SET testo = :testo WHERE id = :id');
            $statement->bindValue(':testo', $_POST['NoteUpdateText']);
            $statement->bindValue(':id', 1);
            $statement->execute();

        // echo a message to say the UPDATE succeeded
        //echo $stmt->rowCount() . " records UPDATED successfully";
        }
    catch(PDOException $e)
        {
        echo $sql . "<br> - IF -" . $e->getMessage();
        }
}

// carica da DB in ogni caso per caricare il P col testo realmente in DB
//$PDO = new PDO('sqlite:myDatabase.sqlite3');

    try {
            $statement = $PDO->prepare('SELECT testo FROM ajax WHERE id=1 LIMIT 1'); 
            $statement->execute(); 

            $row = $statement->fetch();
            //var_dump($row);
            echo $row["testo"];
        }
    catch(PDOException $e)
        {
        echo $sql . "<br> - NORMALE - " . $e->getMessage();
        }       

?>

Answer 1

Why would you override $PDO variable ?

$pdo = new PDO('sqlite:myDatabase.sqlite3');



if( isset($_POST['NoteUpdateText'])  && !empty(trim($_POST['NoteUpdateText'])) ){

  //$testo = $_POST['NoteUpdateText'];

 try {

   $stmt = $PDO->prepare('UPDATE ajax SET testo = :testo WHERE id = :id');
   if ($stmt->execute(array(':testo'=>$_POST['NoteUpdateText'], ':id' => 1)))
   {

     // echo a message to say the UPDATE succeeded
     //echo $stmt->rowCount() . " records UPDATED successfully";
   } else {
     // There's error processing updates
     // debug
     print_r($stmt->errorInfo());
   }
  } catch(PDOException $e) {
    echo $sql . "<br>" . $e->getMessage();
  }
}

// In EVERY case, load the actual DB record and return it to javascript

// There's no need to redeclare $PDO 
// $PDO = new PDO('sqlite:myDatabase.sqlite3');  // --- ISSUE, theoretically this is already opened at line #3 ---

  try {
    $stmt = $pdo->prepare("SELECT testo FROM ajax WHERE id=1 LIMIT 1"); // line #34
   $stmt->execute(); 
   $row = $stmt->fetch();
   //var_dump($row);
   echo $row["testo"];
 } catch(PDOException $e) {
   echo $sql . "<br>" . $e->getMessage();
 }