The mysql error message "Database connection cannot be established" is intermittently showing whenever I call the config file in my page. What seems to be the problem in my code?
///-- config.php --////
$hostname = "localhost";
$database = "db";
$db_user = "root";
$db_pass = "pass";
session_start();
try {
$conn = mysql_connect($hostname,$db_user,$db_pass) or die("Database connection cannot be established.");
if(!$conn)
{
$_SESSION['errormsg'] = "Connection failed.";
exit();
}
else
{
mysql_select_db($database) or die(mysql_error());
}
} catch (Exception $e) {
echo "Exception: ", $e->getMessage(), "\n";
}
die("Database connection cannot be established."); // big deal?
Only tells you what you already know.
die(mysql_error());
Tells you what you need to know.
P.S: intermittently and whenever are contradictory, please update your question to remove the confusion and stress on one.
Related
Here is the code
<?php
$servername = "localhost";
$usrname = "root";
$pwd = "";
$db = "test_db";
// connect to the database
$conn= mysqli_connect($servername, $usrname, $pwd,$db);
if (!$conn){
die('connection failed' . mysqli_connect_error());
}
// Create database
$sql = "CREATE DATABASE IF NOT EXISTS test_db";
if (mysqli_query($conn, $sql)) {
echo "Database created successfully<br>";
} else {
echo "Error creating database: " . mysqli_error($conn);
}
?>
I am not sure what is going on as I am sure i made no errors while typing. As it keeps showing me that there is an unknown database despite the fact i made a CREATE DATABASE statement.
I do not know if there is something else i need to do but by all measures the code should work.
It is supposed to echo the "Database created successfully" or the error message.
`<?php
$servername = "localhost";
$usrname = "root";
$pwd = "";
//$db = "test_db";
// connect to the database
$conn= mysqli_connect($servername, $usrname, $pwd);
if (!$conn){
die('connection failed' . mysqli_connect_error());
}
// Create database
$sql = "CREATE DATABASE IF NOT EXISTS test_db";
if (mysqli_query($conn, $sql)) {
echo "Database created successfully<br>";
} else {
echo "Error creating database: " . mysqli_error($conn);
}
?>`
Your code is fine, You just have to remove $db from mysqli_connect().
Because you are requesting to connect "test_db" to this database which already not exists.
<?php
// Connect to MySQL
$link = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$link) {
die('Could not connect: ' . mysql_error());
}
// Make my_db the current database
$db_selected = mysql_select_db('my_db', $link);
if (!$db_selected) {
// If we couldn't, then it either doesn't exist, or we can't see it.
$sql = 'CREATE DATABASE my_db';
if (mysql_query($sql, $link)) {
echo "Database my_db created successfully\n";
} else {
echo 'Error creating database: ' . mysql_error() . "\n";
}
}
mysql_close($link);
?>
Reference
How do I create a database if it doesn't exist, using PHP?
$conn= mysqli_connect($servername, $usrname, $pwd,$db);
You are trying to connect to a database that did not initially exist, so you get a fatal error.
Try creating new database using try catch blocks
try{
$conn= mysqli_connect($servername, $usrname, $pwd,$db);
}cath(Exception $e){
//your code
}
I just tried to connect a secondary database like this example bellow but i don't know why refuse to work. Any idea?
I mention that each database connection works properly individualy.
$db_HOST = "localhost";
$db_USER = "db_user";
$db_PASS = "db_pass";
$db_NAME1 = "db_test1";
$db_NAME2= "db_test2";
$db_LINK1 = mysql_connect($db_HOST, $db_USER, $db_PASS) or die("Technical revision. Please try again later!");
mysql_select_db($db_NAME1, $db_LINK1) or die("Couldn't select database");
$db_LINK2 = mysql_connect($db_HOST, $db_USER, $db_PASS, true) or die("Technical revision. Please try again later!");
mysql_select_db($db_NAME2, $db_LINK2) or die("Couldn't select database");
Errors i get in the log file:
PHP Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in /config/global/variables.php on line 27
PHP Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in config/global/hello.php on line 3
Thank you!
Do the following (with PDO instead of mysql_connect as the latter is deprecated):
$db_HOST = "localhost";
$db_USER = "db_user";
$db_PASS = "db_pass";
$db_NAME1 = "db_test1";
$db_NAME2= "db_test2";
try {
$db_LINK1 = new PDO('mysql:host='.$db_HOST.';dbname='.$db_NAME1, $db_USER, $db_PASS);
foreach($db_LINK1->query('SELECT * from FOO') as $row) {
print_r($row);
}
$dbh = null;
} catch (PDOException $e) {
print "Error!: " . $e->getMessage() . "<br/>";
die();
}
try {
$db_LINK2 = new PDO('mysql:host='.$db_HOST.';dbname='.$db_NAME2, $db_USER, $db_PASS);
foreach($db_LINK2->query('SELECT * from FOO') as $row) {
print_r($row);
}
$dbh = null;
} catch (PDOException $e) {
print "Error!: " . $e->getMessage() . "<br/>";
die();
}
More info here: php.net/manual/en/pdo.connections.php
If the second connection fails check the exact error message.
You should really use PDO but your code works if you use your link in your db select. For example:
$db1 = mysql_connect($hostname, $username, $password);
$db2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $db1);
mysql_select_db('database2', $db2);
that should work. You forgot to select which database should be used on every link.
I thnk I found the problem.
I forgot to change all queries accordind to the new multiple connection.
LE: Solve confirmed! Thank you all!
I have newly purchased server, on that server database connections are not working.
<?php
error_reporting(E_ALL);
$server = "server name";
$user = "username";
$password = "password";
$db = "test";
echo "Before";
$con = mysql_connect($server, $user, $password);
echo "After";
if (!$con){
die('Could not connect:' . mysql_error());
}
mysql_select_db($db, $con);
?>
When run this file its print Before text but not print After text.
Currently you can use the following code:
ini_set("error_reporting", E_ALL & ~E_DEPRECATED);
Using this you can get either deprecated or not.
FYI: The mysql_* functions have been removed in PHP7.x. There are two modules you can use.
The first is MySQLi, just use the code as follows:
<?php
$con = mysqli_connect("localhost","my_user","my_password","my_db");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>
You can also use PDO using code :
<?php
$servername = "localhost";
$username = "username";
$password = "password";
try {
$conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo "Connected successfully";
}
catch(PDOException $e)
{
echo "Connection failed: " . $e->getMessage();
}
?>
I'm running the following very basic PDO:MySql connection:
<?php
$host = '127.0.0.1:8888';
$db = 'communities';
$user = 'root';
$pass = 'yY5MF)q/DCzc';
// Create connection
try {
$conn = new PDO('mysqli:host=$host;dbname=$db', $user, $pass);
foreach($conn->query('SELECT * from city_detail') as $row) {
print_r($row);
}
$conn = null;
// Check connection
} catch (PDOException $e) {
print "Error!: " . $e->getMessage() . "<br/>";
die();
}
echo "Connected successfully";
?>
I've modified php.ini to allow for extension=php_pdo_mysql.dll with no effect. Is there something else that I'm missing. I am using PHP7.0.3. The error message output is Error!: could not find driver Kudos!
You need to use double quotes to get variable data inside string:
$conn = new PDO("mysqli:host=$host;dbname=$db", $user, $pass);
The problem was using msqli instead of mysql.
I am new to PHP and need to modify some code in order to compile with my Microsoft SQL Server. The original code is like this. I downloaded it from usercake
<?php
/*
UserCake Version: 2.0.2
http://usercake.com
*/
//Database Information
$db_host = "localhost"; //Host address (most likely localhost)
$db_name = "202"; //Name of Database
$db_user = "202"; //Name of database user
$db_pass = "password"; //Password for database user
$db_table_prefix = "uc_";
GLOBAL $errors;
GLOBAL $successes;
$errors = array();
$successes = array();
/* Create a new mysqli object with database connection parameters */
$mysqli = new mysqli($db_host, $db_user, $db_pass, $db_name);
GLOBAL $mysqli;
if(mysqli_connect_errno()) {
echo "Connection Failed: " . mysqli_connect_errno();
exit();
}
//Direct to install directory, if it exists
if(is_dir("install/"))
{
header("Location: install/");
die();
}
?>
I already installed sqlsrv and tested the link. It works with my database. Then I changed the code to this:
<?php
//Database Information
$server = "servername";
$connectionInfo = array("Database"=>"databasename","UID"=>"xxxxxx", "PWD"=>"xxxxxx" );
$db_table_prefix = "uc_";
GLOBAL $errors;
GLOBAL $successes;
$errors = array();
$successes = array();
/* Create a new sqlsrv object with database connection parameters */
$mssqlsrv = new sqlsrv($server, $connectionInfo);
GLOBAL $mssqlsrv;
if(sqlsrv_connect_errno()) {
echo "Connection Failed: " . sqlsrv_connect_errno();
exit();
}
//Direct to install directory, if it exists
if(is_dir("install/"))
{
header("Location: install/");
die();
}
?>
I get the following error message:
Fatal error: Class 'mssql' not found in
I think this line is the problem:
$mssqlsrv = new sqlsrv($server, $connectionInfo);
But I do not know how to fix this.
I would use PDO in this case: http://www.php.net/manual/en/pdo.construct.php
You can create a DSN connection to SQL Server
$dsn = "sqlsrv:Server=servername;Database=databasename"
$user = 'dbuser';
$password = 'dbpass';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
The information to connect to SQL server is available here: http://www.php.net/manual/en/ref.pdo-sqlsrv.connection.php