使用php连接到mysql

Here is my following tutorial code from "Learning PHP MYSQL and Javascript" by OReilly.

<?php 
//require_once = 'login.php';

$db_database = 'publications';
$db_hostname = 'localhost:8888';
$db_username = 'root';
$db_password = 'root';


$db_server = mysql_connect($db_hostname, $db_username, $db_password);
if(!$db_server) die("Unable to connect to MYSQL: ". mysql_error());

mysql_select_db($db_database)
    or die("Unable to connect to database: " . mysql_error());

$query = "SELECT * FROM classics";
$result = $mysql_query($query);

if(!$result) die ("Could not query: " . mysql_error());
$rows = mysql_num_rows($result);

for($j = 0; $j < $rows; ++$j)
{
    echo 'Author: ' . mysql_result($result, $j, 'author') . '</br>';
    echo 'Title: ' . mysql_result($result, $j, 'title'). '</br>';
    echo 'ISBN: '.mysql_result($result, $j, 'isbn').'</br>';
}

?>

However, I'm getting an error when trying to connect. The browser says it's a 500 error (which really isn't that helpful). When I take out the lines $db_username = 'root'; $db_password = 'root'; I get another error saying: "Unable to connect to database: Access denied for user ''@'localhost' to database 'publications'".

Can anyone help diagnose the problem?

Thanks!

Change this

$result = $mysql_query($query);

to this

$result = mysql_query($query);

Function name is mysql_query not $mysql_query, $ is used in variable names.

Also, instead of trying to "see" your code immediately in a browser window you could use a PHP command line instead. If your file is called foo.php you coudl do:

>> php foo.php
PHP Notice:  Undefined variable: mysql_query in /var/www/foo.php on line 17
PHP Fatal error:  Function name must be a string in /var/www/foo.php on line 17

As you see, the error message is pretty clear. Because of using $mysql_query it thinks that mysql_query is a variable, but such a variable is not defined somewhere.

Do you try connecting manually to your db by connection infor u set up in code,

use phpmysql to connect to db first , change phpmysql config file to match the mysql server authentication infor, then ensure all are right before coding anything further.

please write this

mysql_select_db($db_database, $db_server)

instead of

mysql_select_db($db_database)

And write this

$result = mysql_query($query);

instead of

$result = $mysql_query($query);

One more thing please check your host name :$db_hostname = 'localhost:8888';

By general it is $db_hostname = 'localhost:8080';

So please confirm one more time

$ symbol should be used only for variables not for functions

$var=5;// variable declaration

if you want to declare function syntax $ should not be used
Ex:

$function_var = mysql_query($query);

In this function_var is variable and mysql_query($query) is function.

Stop using mysql_connect()!

You should not use this or other related functions related to this extension.

It's depreciated and removed in PHP 7.0.0 and beyond. An alternative is using PDO or MySQLi. Below is an example script for connecting to MySQL using PDO:

<?php

  /* Connect to a MySQL database using driver invocation */

  /* DSN options:
     http://php.net/manual/en/ref.pdo-mysql.connection.php

     Error handling options:
     http://php.net/manual/en/pdo.error-handling.php

     Learn how to secure against SQL injection attacks:
     http://php.net/manual/en/pdo.prepared-statements.php
  */

  $user = 'myusername';
  $pass = 'mypassword';
  $host = 'localhost';
  $mydb = 'mydatabase';

  $dsn = "mysql:dbname=$mydb;host=$host"; 

  try {
      $dbh = new PDO($dsn, $user, $pass);
  } catch (PDOException $e) {
      echo 'Connection failed: ' . $e->getMessage();
  }

?>

you can do it like below:

<?php
    $conn = mysqli_connect("localhost","root","");
    if (!$conn)
    {
        die("Connection failed:".mysqli_connect_error());
    }
    $db = mysqli_select_db($conn,"Database_name");
    if(!$db)
    {
        echo "Connection failed";
    }
?>