How to display string by php id ?id=1?

M

MentozZz ORG2021-08-29 07:04:37

PHP

MentozZz ORG, 2021-08-29 07:04:37

Good afternoon, I just started learning the php and mysql language

and I had a question how to display a certain string, say with id 1 or 2

, example site.com/?id=1 or site.com/?id=2

here is my code that I received for 50 minutes of evolution

<?php
include 'config.php'; // получили соединение с бд

$result = mysqli_query($link,"SELECT * FROM `product`") ;



?>

<!DOCTYPE html>
<html dir="ltr">
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>

  <table border='1'>
  <tr>
    <td>Идентификатор</td>
    <td>Наименование</td>
    <td>Цена</td>
  </tr>
  <?php
    while($prod = mysqli_fetch_assoc($result))
    {
        ?>
        <tr><td><?php echo $prod['id']; ?></td><td><?php echo $prod['name']; ?></td><td><?php echo $prod['price']; ?> </td></tr>
        <?php
    }
  ?>
</table>

  </body>
</html>

if it's not difficult to show directly on my code

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3 answer(s)

F

FanatPHP, 2021-08-29
@Gor_Ohanyan

The question is good, but here we run into the main problem of PHP - ALL tutorials on the Internet, and especially videos - show how to write hellish code from the last century.
1. Getting the value from the address bar
To get the value of the variable that was passed in the query string (this is the one after the question mark), you need to refer to the $_GET variable.
That is, in this case, you can write $id = $_GET['id']. The name of the received variable ($id) can be anything and does not have to match the passed value. But in the $_GET array index, of course, you need to write exactly the name that is in the address bar. That is, if site.com/?id=1, then $_GET['id'] will have the value 1.
2. Data validation
Further, it is very desirable to check that we got what we wanted in the variable, and also that we got at least something at all.
First, you need to check if the $_GET array contains the required key. In this case, this can be done using the isset () operator (although in general it is not recommended for checking the presence of keys in arrays)
. error.
Then, since id can only be an integer greater than zero, it's better to check that too and throw an error too.
3. Connecting to the database.
in "config.php" it should not be written what is there now, but this (with its own connection parameters, of course)

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$link = mysqli_connect($host, $user, $pass, $db_name);
$link->set_charset("utf8mb4");

4. SQL
The query we need looks like this:
SELECT * FROM `product` WHERE id=1
5. Executing the query in PHP
But of course, instead of 1, you need to substitute the value of the variable.
This is the hardest part. But you need to learn it once and then apply it everywhere
. It is important that the data in the database always gets separately from the request itself. This is an immutable rule that must always be observed.
For this you need

Replace all variables in the request with special markers called placeholders or parameters, but in fact - just question marks
Prepare the request for execution using the prepare() function. This function accepts a query string and returns an instance of the special class stmt, with which all further manipulations are performed
Bind variables to the request.
Execute the previously prepared query with execute()
Get the query result via get_result()
and then a specific row from the database using the already familiar fetch_assoc

In code it will be like this

$sql = "SELECT * FROM `product` WHERE id=?";
$stmt = $link->prepare($sql);
$stmt->bind_param("s", $id);
$stmt->execute();
$result = $stmt->get_result();
$row = $result->fetch_assoc();

bind_param() takes as parameters all the variables that should be included in the request, in the same order as the placeholders in the request. But in addition, the types for all variables must first be specified in this function, as a string, where the type of the variable is denoted by a single letter. That is, there should be exactly as many letters in this line as there will be variables further. Luckily, you don't have to worry too much about types and specify the type "s" for all variables.
6. Data output.
It is important to understand that at the time of data output, there should no longer be any work with the database!
There should only be PHP variables with data already acquired.

Z

zombtron, 2021-08-29
@zombtron

$id = intval($_GET['id']);
SELECT * FROM `product` WHERE `id` = $id

M

Maxim Komarov, 2021-08-29
@qwnofear

#dell.