How to Update MYSQL table in PHP using JSON - php

Question

I am working with jstree. The tree works fine.I send JSON to a PHP file with JQuery. This works fine.
$("#button3").click(function(){
//json object
var objtree = $("#container").jstree(true).get_json('#', { 'flat' : true });
var fulltree = JSON.stringify(objtree);
var myarray = $.parseJSON(fulltree);
var params = { myarray: myarray };
var paramJSON = JSON.stringify(params);
//sending to php file
$.post('update.php',{ data: paramJSON });
});
Then in the php file (update.php), I update mySQL table by: deleting all the records in $tablename ($sql1) and inserting the information gotten from the JSON ($sql2). This works fine.
<?php
$connection = mysqli_connect($servername, $user,$password,$database) or die("Error " . mysqli_error($connection));
$test = $_POST["data"];
$obj = json_decode($test, true);
$data = $obj["myarray"];
//first query
$sql1 = "DELETE FROM $tablename";
$connection ->query($sql2);
foreach($data as $val){
//second query
$sql2 = "INSERT INTO $tablename(id,parent,text) VALUES('".$val['id']."', '".$val['parent']."', '".$val['text']."')";
$result = mysqli_query($connection, $sql) or die("Error in Selecting " . mysqli_error($connection));
}
mysqli_close($connection);
?>
But what I want is not to delete everything in the table then insert them brand new. But an SQL statement to update the old values (using the id maybe?) and insert the new values.
So like:
If id exists:
update row
else:
insert new row
I am new to PHP and SQL. So my problem is knowing the PHP syntax for accessing JSON array information. So please any example would be much appreciated!

Answer 1

First, you'll use a PHP function to get all rows matching the given ID. if this returns one, you'll use another function to UPDATEwhere the ID == valueFromPreviousFunction, else you'll call a function to INSERT a new row.

Answer 2

$check = mysqli_query($connection,"SELECT * FROM `your_table_name` WHERE `id`='".$val["id"]."'");
if(mysqli_num_rows($check)==1)
{
//Update the row
$update = mysqli_query($connection,"UPDATE `table_name` SET `parent`='".$val["parent"]."', `text`='".$val["text"]."' WHERE `id`='".$val["id"]."'");
}
else
{
//Insert the row
}

Answer 3

There isn't a command to do what you want in a single operation.
You should either fetch all ids beforehand and run an update for each one of them separately, or use REPLACE INTO.
Be careful with REPLACE INTO, though: if a row matching a primary/unique key exists, it first deletes it and then inserts a new one rather than updating the existing row.