Mysqli query in function - PHP

问题:

I have a list of functions in functions.php. I'm upgrading from Mysql to Mysqli because I just learning Mysql is now depreciated.

I declare my connection in a top levelconnect.php file. The first file required.

Anyway back to the point all my functions use mysql_query("QUERY") and that always worked fine. Now I changed all the them to:

$con->query("QUERY") // ($con is my connection variable)

Now I'm getting a Fatal error: Call to a member function query() on a non-object in C:\wamp\www\PHP\functions.php on line 241.

So I don't get why I can query if I'm declaring my variable in my whole file. It should be accessible everywhere, I'm just not sure. This has put my website on hold, until I can fix this. Here is a sample function from functions.php

function getSiteName()
{
    $row = $con->query("SELECT * FROM siteinfo")->fetch_array();
    return $row["siteName"];
}

My connection:

global $con ;
$con = new mysqli("localhost", "itunes89", "XXXX","projectanvil") or die("Sorry, were having server connection issues. Please try again later.");

Thanks guys! :D My site where I'm having this error

回答1:

That's a variable scope problem. You need to pass $conn to getSiteName():

function getSiteName($con) {
    $row = $con->query("SELECT * FROM siteinfo")->fetch_array();
    return $row["siteName"];
}

$name = getSiteName($con);

Or using a class with constructor injection:

class MyThing
{
    protected $con;

    public function __construct($con) {
        $this->con = $con;
    }

    public function getSiteName() {
        $row = $this->con->query("SELECT * FROM siteinfo")->fetch_array();
        return $row["siteName"];
    }
}

$obj = new MyThing($con);
$name = $obj->getSiteName();

Throughout the class you can use $this->con to access the connection.

回答2:

  $con = new mysqli(
         "localhost", 
         "itunes89", 
          "XXXX",
          "projectanvil"
  );

Will not return null or false on failure.

You should check value of

  mysqli_connect_errno()

After connection to verify that $con is valid server connection.

Since you made $con global, to make getSiteName function access it you should write:

 function getSiteName(){
 global $con;
      $row = $con->query("SELECT * FROM siteinfo")->fetch_array();
      return $row["siteName"];
 }

回答3:

Do you defind for $con object

<?php
// connect to the server
$conn = new mysqli('localhost', 'root', 'pass', 'dbname');

// check connection
if (mysqli_connect_errno()) {
  exit('Connect failed: '. mysqli_connect_error());
}
?>