PHP not updating rows in Database
Question
What am I doing wrong here. I can't figure out how to make the Update block work. When I hit "Update" button, it goes back to edit.php but with
errors. Errors are: Notice: Undefined variable: POST in C:\\xampp\\htdocs\\libSys\\edit.php on line 45
Notice: Undefined variable: POST in C:\\xampp\\htdocs\\libSys\\edit.php on line 46
Notice: Undefined variable: id in C:\\xampp\\htdocs\\libSys\\edit.php on line 48
Successfully Updated
Lines 45, 46, 48 has
echo $author = $POST['author']; //line 45
echo $isbn = $POST['isbn']; //line 46
$sql = "UPDATE booklist SET Author='$author', Title='title', ISBN = '$isbn' WHERE ID = '$id' "; //line 48
The complete code of edit.php are below:
<?php
include('databaseConnection.php');
?>
<html>
<head>
<link rel="stylesheet" type="text/css" href="./css/librarySystem.css">
<title> Edit Book Information </title>
</head>
<div>
<?php
if(isset($_REQUEST['edit'])) //FIRST IF
{
$id = $_REQUEST['edit'];
$sql_select = "SELECT * FROM booklist WHERE ID=$id";
$result=mysql_query($sql_select);
// collect all the data using mysql_fetch_array and assign to our $variables
while($row = mysql_fetch_array($result))
{
$id = $row['ID'];
$title = $row['Title'];
$author= $row['Author'];
$yearLevel = $row['YearLevel'];
$isbn = $row['ISBN'];
}
//displays form for user to edit book information
echo "<form method='POST' action='edit.php'>";
echo "Enter New or Correct Title: <input type='text' name='title' value='$title' > <br />";
echo "Enter New or Correct Author: <input type='text' name='author' value='$author'> <br />";
echo "Enter New or Correct ISBN: <input type='text' name='isbn' value='$isbn' > <br / >";
echo "<input type='submit' name='save' value='Update' > <br />";
echo "</form>";
} //END 1st IF
else if( isset($_POST['save'] ) )
{
echo $title = $_POST['title'];
echo $author = $POST['author'];
echo $isbn = $POST['isbn'];
$sql = "UPDATE booklist SET Author='$author', Title='title', ISBN = '$isbn' WHERE ID = '$id' ";
$result = mysql_query($sql);
if($result == true)
{
echo "Successfully Updated" ;
}
//header('Location: ./booklist.php');
}
?>
How can I correct the update block. It seems to be going to the if(isset($_POST['save']) when I hit "Update" but won't really update the row. Please help. I'm stuck. I don't understand why the "Undefined variable" error pops when I have the variables assigned with $_POST['author']...
I'd appreciate any help or explanation. Thanks.
5 answers
solution1
2 ACCPTED 2015-11-02 12:41:12
Use super global variables as $_POST[]
echo $author = $_POST['author'];
echo $isbn = $_POST['isbn'];
Before updated into database use mysql_real_escape_string
$author=mysql_real_escape_string($author),
$isbn=mysql_real_escape_string($isbn));
$sql = "UPDATE `booklist` SET Author='".$author."', Title='title', ISBN = '".$isbn."' WHERE ID = $id";
Note
mysql is deprecated instead use mysqli OR PDO
solution2
0 2015-11-02 12:40:44
Change this line
echo $author = $POST['author'];
echo $isbn = $POST['isbn'];
to
echo $author = $_POST['author'];
echo $isbn = $_POST['isbn'];
solution3
0 2015-11-02 12:42:03
you have a syntax error, you use $POST instead of $_POST.
echo $author = $_POST['author']; //line 45
echo $isbn = $_POST['isbn']; //line 46
$sql = "UPDATE booklist SET Author='$author', Title='title', ISBN = '$isbn' WHERE ID = '$id' "; //line 48
solution4
0 2015-11-02 12:43:01
The syntax for php POST global variable is $_POST not $POST that you are using.
And I guess you are getting $id from a form using $_GET or $_POST method only. So check out those syntaxes as well.
solution5
0 2015-11-02 12:54:03
There are a couple of errors in the code. Firstly, $_POST is a superglobal in php. Superglobals start with a dollar sign and an underscore. You forgot the underscore that's why it's undefined. rewrite as:
echo $author = $_POST['author'];
echo $isbn = $_POST['isbn'];
Secondly, you're using the $id variable inside the quotes. Rewrite line 48 as:
$sql = "UPDATE booklist SET Author='{$author}', Title='title', ISBN = '{$isbn}' WHERE ID = '{$id}' "; //line 48
To use variables inside quotes without concatenation, you can use the '{' bracket. Keep in mind though, you can't do the same with constant values. Hope this helps :)
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