Mysterious behaviour of php - php

Question

Below code works as expected. It adds 3 entries to the table 'keywords'.
<?php
include "config.php";
try{
// $conn = new PDO(DBINFO,USER,PASS);
// $sql = "INSERT INTO projects (title,duration, startyear, description, tags,email) VALUES (:title,:duration, :startyear, :description, :tags,:email)";
// $stmt = $conn->prepare($sql);
// $stmt->bindParam(':title', $_POST['title'],PDO::PARAM_STR);
// $stmt->bindParam(':email', $_POST['email'], PDO::PARAM_STR);
// $stmt->bindParam(':duration', $_POST['duration'], PDO::PARAM_STR);
// $stmt->bindParam(':startyear', $_POST['startyear'], PDO::PARAM_STR);
// $stmt->bindParam(':description', $_POST['description'], PDO::PARAM_STR);
// $stmt->bindParam(':tags', $_POST['tags'], PDO::PARAM_STR);
// $stmt->execute();
for($i=0; $i<3; $i++){
$conn2 = new PDO(DBINFO,USER,PASS);
$sql2 = "INSERT INTO keywords (keyword,confidence) VALUES (:keyword,:confidence)";
$stmt2 = $conn2->prepare($sql2);
$a = 'asdfds';
$stmt2->bindParam(':keyword', $a,PDO::PARAM_STR);
$stmt2->bindParam(':confidence', $a, PDO::PARAM_STR);
$stmt2->execute();
}
}
catch(PDOException $pe){
die("Could not connect to the database :".$pe->getMessage());
}
?>
However, when I run the below code (where I uncommented the first part), the entries get added 6 times to the 'keywords' table.
<?php
include "config.php";
try{
$conn = new PDO(DBINFO,USER,PASS);
$sql = "INSERT INTO projects (title,duration, startyear, description, tags,email) VALUES (:title,:duration, :startyear, :description, :tags,:email)";
$stmt = $conn->prepare($sql);
$stmt->bindParam(':title', $_POST['title'],PDO::PARAM_STR);
$stmt->bindParam(':email', $_POST['email'], PDO::PARAM_STR);
$stmt->bindParam(':duration', $_POST['duration'], PDO::PARAM_STR);
$stmt->bindParam(':startyear', $_POST['startyear'], PDO::PARAM_STR);
$stmt->bindParam(':description', $_POST['description'], PDO::PARAM_STR);
$stmt->bindParam(':tags', $_POST['tags'], PDO::PARAM_STR);
$stmt->execute();
for($i=0; $i<3; $i++){
$conn2 = new PDO(DBINFO,USER,PASS);
$sql2 = "INSERT INTO keywords (keyword,confidence) VALUES (:keyword,:confidence)";
$stmt2 = $conn2->prepare($sql2);
$a = 'asdfds';
$stmt2->bindParam(':keyword', $a,PDO::PARAM_STR);
$stmt2->bindParam(':confidence', $a, PDO::PARAM_STR);
$stmt2->execute();
}
}
catch(PDOException $pe){
die("Could not connect to the database :".$pe->getMessage());
}
?>
I can't understand this. Any help?

Answer 1

Why do you create 4 different connections to the same server and schema in the first place?
The loop creates connections and closes them automatically when the references to statements and connections are overwritten.
But the original connection from before the loop will stay open and is reused for the statements. If you create a third connection without closing it before the loop you'll end up with 9 entries.
So delete the references to connection objects if they are no longer needed (this includes associated statements).
Or better yet reuse connections instead of creating a new connection for every statement.