PHP/MySQL Database/mysqli connect

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custom-error-messages.php

 
$errors = array (
          "1045" => "Unable to authenticate user.",
          "2005" => "Unable to contact the MySQL server.",
          "2013" => "Lost MySQL connection."
                );
$link = @mysqli_connect("127.0.0.1", "root","", "mydatabase");
if (!$link) {
   $errornum = mysqli_connect_errorno();
   echo $errors[$errornum];
}



Discovering Which Extension Is Being Used

 
<?php
  function mysqlinstalled (){
    if (function_exists ("mysql_connect")){
      return true;
    } else {
      return false;
    }
  }
  function mysqliinstalled (){
    if (function_exists ("mysqli_connect")){
      return true;
    } else {
      return false;
    }
  }
  
  if (mysqlinstalled()){
    echo "<p>The mysql extension is installed.</p>";
  } else {
    echo "<p>The mysql extension is not installed..</p>";
  }
  if (mysqliinstalled()){
    echo "<p>The mysqli extension is installed.</p>";
  } else {
    echo "<p>The mysqli extension is not installed..</p>";
  }
?>



function mysql_connect() establishes an initial connection with the MySQL server.

 
int mysql_connect([string hostname [:port] [:/path/to/socket] [, string username][, string password])

<?
@mysql_connect("localhost", "web", "aaaa") or die("Could not connect to MySQLserver!");
?>
In this case, localhost is the server host, web is the username, and aaaa is the password. 
The @ will suppress any error message that results from a failed attempt.



In PHP 5 using the MySQLi extension

 
<?php
    $mysqli = mysqli_connect("localhost", "root", "","mydatabase", 3306);
    $result = mysqli_query($mysqli, "SELECT * FROM mytable");
    while($row = mysqli_fetch_array($result)) {
        foreach($row as $key => $value) {
            echo "$key = $value</BR>\n";
        }
    }
    mysqli_free_result($result);
    mysqli_close($mysqli);
?>



MySQL Connection Test

 
<html>
 <head> 
  <title>MySQL Connection Test</title> 
 </head>
 <body>
  <h2>
   <?php $connection = mysql_connect( "localhost", "root", "" )
   or die( "Sorry - unable to connect to MySQL" );
   echo( "Congratulations - you connected to MySQL" );
   ?>
  </h2>
 </body>
</html>
Источник — «http://wbex.ru/index.php?title=PHP/MySQL_Database/mysqli_connect&oldid=1087»