write database connection code in many files

Question

There are many files [ file1.php, file2.php ] in our project & i wrote database connection code in many files instead of single file [ database.php ] , is there any problem with that ?

if it is wrong than please help me what code i need to change in file1.php to connect to database.php

Below 2 lines i used in file1.php

$con=mysqli_connect('localhost', 'root', 'gfgf', 'g');
if ($result=mysqli_query($con,$sql))

Instead of above 2 lines, is it correct to use below 2 lines ?

require_once("database.php");
$db_handle = new DBController();

file1.php

<?php

require_once("database.php");
$db_handle = new DBController();

$con=mysqli_connect('localhost', 'root', 'gfgf', 'g');

if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  } 

$todaydate=date('Y-m-d');

$sql="SELECT * FROM orders WHERE importdate >= NOW() - INTERVAL 1 DAY";

    if ($result=mysqli_query($con,$sql))
  {

  $rowcount=mysqli_num_rows($result);

  printf("Uploaded - %d rows.\n",$rowcount);

  // Free result set
  mysqli_free_result($result);
  }

mysqli_close($con);


?>  

Answer 1

database connection code in many files instead of single file, is there any problem with that?

Nothing critical, but what if your database credentials would change? Are you going to edit all these files?

is it correct to use below 2 lines ?

Yes, apart from the fact that DBController doesn't seem to belong here. Where did you get that and why do you think it is needed?

Besides, in your example you seem to be using both ways, including database.php and writing the connection code right in the script. You should use only one method.

there are other issues in your code

• you should never ever use a code like echo "Failed to connect to MySQL: " . mysqli_connect_error();. Read my article on the proper error reporting
• same goes for the if ($result=mysqli_query($con,$sql)) condition. It effectively mutes the possible error message which will never reach you. You should never run a query inside a condition like that. Just let the error go.
• you should never ever select all rows from a database only to count them. Ask a database to count the rows instead.