title: Why do we have to close the MySQL database after a query command?
body: <p>I'm starter.</p>
  
  <p>I want to know what will happen if we don't close the MySQL connection.</p>
  
  <p>1- Is it possible to open more than one database if we don't close them? I mean can we open more than one database in a same time?</p>
  
  <p>2- Does closing database increase the speed?</p>
  
  <p>3- Is it necessary to close the database or it is optional?</p>
  
  <p>Look at this code. I don't use "mysql_close()" so I don't close the database after each request. There are a lot of requests for this PHP page. Maybe 50000 per each minute. I want to know closing database is necessary for this code or no?</p>
  
  <pre><code>&lt;?php   
  //Include the file that lets us to connect to the database.
  include("database/connection.php");
  
  //Call "connect" function to connect to the database.
  connect("database", "localhost", "root", "", "user");
  
  //The GPRS module send a string to this site by GET method. The GPRS user a variable named variable to send the string with.
  $received_string = $_GET["variable"];
  
  //Seprates data in an array.
  $array_GPRS_data = explode(",", $received_string);
  
  //we need to remove the first letter.
  $array_GPRS_data[9] = substr($array_GPRS_data[9], 1);
  
  
  $array_GPRS_data[13] = substr($array_GPRS_data[13], 4, 2).substr($array_GPRS_data[13], 2, 2).substr($array_GPRS_data[13], 0, 2);
  
  //Query statement.
  $query = "INSERT INTO $array_GPRS_data[17](signal_quality, balance, satellite_derived_time, satellite_fix_status, latitude_decimal_degrees,
  latitude_hemisphere, longitude_decimal_degrees, longitude_hemisphere, speed, bearing, UTCdate, theChecksum)
  VALUES('$array_GPRS_data[0]', '$array_GPRS_data[1]', '$array_GPRS_data[5]', '$array_GPRS_data[6]', '$array_GPRS_data[7]',
  '$array_GPRS_data[8]', '$array_GPRS_data[9]', '$array_GPRS_data[10]', '$array_GPRS_data[11]', '$array_GPRS_data[12]', '$array_GPRS_data[13]',
  '$array_GPRS_data[16]')";
  
  //Run query.
  $result = mysqli_query($query);
  
  //Check if data are inserted in the database correctly.
  if($result)
  {
      echo("*#01");
  }
  else
  {
      echo("Error: 001");
      echo (mysqli_error());
  }   
  ?&gt;
  </code></pre>