PHP : $_GET is not retrieving data from MySQL database

Question

I have a blog-type php site with mysql database. This blog have some lessons. There's a table "lessons", which contain id, title, text of lesson, etc. When I display the last lessons on the main page, it works just right.

I connect to db like this:

<?php 
$db = mysql_connect ("localhost", "root", "");
mysql_select_db("kursach", $db);
mysql_query("SET NAMES utf8");

$result = mysql_query ("SELECT title, meta_k, meta_d, text FROM settings
WHERE page='index' ", $db);

$myrow = mysql_fetch_array($result);
?>

and display them using loop:

<?php 
$result = mysql_query("SELECT id, title, date, description FROM lessons", $db);

$myrow = mysql_fetch_array($result);
do {
  printf ("<div class='right-column-content'>
    <div class='right-column-content-heading'>
      <a href='lesson_view.php?%s'><h1>%s</h1></a>
      <h2>%s </h2>
    </div>
    <div class='right-column-content-content'>
      <p>%s</p>
      <div class='button'><a href='lesson_view.php?%s' >Читати далі</a></div>
    </div>
  </div>", $myrow['id'], $myrow["title"], $myrow["date"], $myrow["description"], $myrow["id"]);
}
while($myrow = mysql_fetch_array($result))
 ?>

I also have a file for full content of the lesson - lesson_view.php. As you can see at the code above, i send the id of lesson to link to this lesson:

  lesson_view.php?%s
  $myrow["id"]

In the lesson_view.php I connect to db and get the id like this:

<?php 
$db = mysql_connect ("localhost", "root", "");
mysql_select_db("kursach", $db);
mysql_query("SET NAMES utf8");

if (isset($_GET['id'])) {$id = $_GET['id'];}

$result = mysql_query("SELECT * FROM lessons WHERE id = '$id' ", $db);

$myrow = mysql_fetch_array($result);
?>

And use this code to display the data:

<div class="right-column-content">
    <div class="right-column-content-heading">
      <h1><?php echo $myrow['title'] ?></h1>
      <h2><?php echo $myrow['date'] ?> </h2>
      <h2><?php echo $myrow['author'] ?> </h2>
    </div>
    <div class='right-column-content-content'>
      <p><?php echo $myrow["text"] ?></p>
    </div>
  </div>

The problem is, when I try to look the full content of lesson (for exaple, /lesson_view.php?1), it doesn't display any data: no title, no text, nothing. I've tried this query directly at MySQL and it works, so, maybe there's some error in php code that I can't find. Will be thankful for any help.

P.S. I'm a beginner at php.

Your if logic is flawed, in lesson_view.php your query and execute of query should be put inside of the if sentence, because if your $id isn't set in the if clause you will still get a "Notice undefined" because you are calling the $id which isn't set. (And it will most likely cause your query to fail) - Also, you should change from mysql to mysqli or PDO no reason to learn a deprecated / bad habbits from the start. — Epodax
– Epodax, Commented Dec 23, 2015 at 7:52

Armen · Accepted Answer · 2015-12-23 07:51:40Z

2

if you want to have in $_GET id then your link should be instead lesson_view.php?%s -> lesson_view.php?id=%s

for example lesson_view.php?id=5 mean that $id = $_GET['id'] will give 5, $id = 5;

answered Dec 23, 2015 at 7:51

Armen

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Alan Tan · Accepted Answer · 2015-12-23 07:52:24Z

1

<a href='lesson_view.php?%s'><h1>%s</h1></a>

You did not name the 'id' variable.

Change the links to

<a href='lesson_view.php?id=%s'><h1>%s</h1></a>

answered Dec 23, 2015 at 7:52

Alan Tan

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Comments

devpro · Accepted Answer · 2015-12-23 08:02:29Z

0

The only issue is that your printf() have 5 arguments and you are using only four and fourth one is description that you are using here

<div class='button'><a href='lesson_view.php?%s' >Читати далі</a></div>

Solution is that:

printf ("<div class='right-column-content'>
<div class='right-column-content-heading'>
<a href='lesson_view.php?%s'><h1>%s</h1></a>
<h2>%s </h2>
</div>
<div class='right-column-content-content'>
<p>%s</p>
<div class='button'><a href='lesson_view.php?id=%s' >Читати далі</a></div>
</div>
</div>", $myrow['id'], $myrow["title"], $myrow["date"], $myrow["id"], $myrow["description"]);

Move $myrow["id"] in fourth position you will get the ID as query string.

And also add the id in query string.

answered Dec 23, 2015 at 8:02

devpro

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1 Comment

devpro Over a year ago

@artur-komendacki: just change second arguments

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