PHP Function Accessing Database Connection

问题:

How do I allow a function to access a database connection without using GLOBAL?

config.php

 DEFINE ('DB_HOSTNAME', 'hostname');
 DEFINE ('DB_DATABASE', 'database');
 DEFINE ('DB_USERNAME', 'username');
 DEFINE ('DB_PASSWORD', 'password');

 $dbc = mysqli_connect(DB_HOSTNAME, DB_USERNAME, DB_PASSWORD, DB_DATABASE);

 if(!$dbc) die("Unable to connect to MySQL: " . mysqli_error($dbc));

functions.php

 function something()
 {
 $info = mysqli_query($dbc, "SELECT info FROM text") or die("Error: ".mysqli_error($dbc));
 }

The above gives me the following error: mysqli_query() expects parameter 1 to be mysqli, null given in

回答1:

Use function parameters

function something ($dbc) {
  // your db code here
}

function arguments

回答2:

Either pass the database handle to your function, as @KingCrunch and others have said, or call a function that returns the handle:

In config.php:

function get_dbc() {
    $dbc = mysqli_connect(DB_HOSTNAME, DB_USERNAME, DB_PASSWORD, DB_DATABASE);
    if(!$dbc) die("Unable to connect to MySQL: " . mysqli_error($dbc));
    return $dbc;
}

In functions.php:

require_once('config.php');

function something()
{
    $dbc = get_dbc();
    $info = mysqli_query($dbc, "SELECT info FROM text") or die("Error: ".mysqli_error($dbc));
}

You may wish to look at The mysqli Extension and Persistent Connections for details on how you can prevent the connection from being re-established on each call to get_dbc(). There are alternative approaches to this, such as creating a singleton class for your database connection.

回答3:

There are two ways one is by passing arguments and the other by using function closure like @Ondrej said. But I wonder both of these require you to modify the code if that is the case, then I would suggest you to use global keyword.

You can use global keyword to get the scope of variable $dbc

Try this..

function something()
{
   global $dbc;
   $info = mysqli_query($dbc, "SELECT info FROM text") or die("Error: ".mysqli_error($dbc));
}

(OR)

Try this...

function something()
{
    $dbc = func_get_arg(0);
     $info = mysqli_query($dbc, "SELECT info FROM text") or die("Error: ".mysqli_error($dbc));
}

& do this ....

$query = something($dbc);

回答4:

There are more ways. You could use classic procedural style:

function something($dbc)

or anonymous function (if you use PHP5.3):

$fn = function() using ($dbc)

回答5:

its so simple just pass your $conn variable into another calling function(instead of making new connection) like

yourpage.php

$conn = new mysqli($servername, $username, $password, $dbname);
someFunction ($conn)//you can add other parameters if you like 

function someFunction ($conn) {
    $result = mysqli_query ($conn, "SELECT * FROM examples);
}

Note:This is not good practice to always make new connection for database access.so always make connection once and use it every where.(but if your requirement different and require multiples connections then you can make multiples connections)