Warning: mysqli_query() expects parameter 1 to be mysqli, null given in PHP [duplicate]

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I'm having trouble with using a mysqli_query inside a function, error: Warning: mysqli_query() expects parameter 1 to be mysqli, null given . If I var_dump($dbc) outside of the function I get the expected result but when I use it inside the function I get NULL returned.

Here is my connection script:

define('DB_HOST', 'localhost');
define('DB_DBNAME', 'db');
define('DB_USER', 'root');
define('DB_PASSWORD', 'root');

$dbc = @mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_DBNAME)or die(mysqli_error($dbc));

Here is my function:

function memInfo($var1, $var2){
    var_dump($dbc);
    $query = mysqli_query($dbc, "SELECT * FROM `members` WHERE id = '".$var1."'")or die(mysqli_error($dbc));
    $rowCount = mysqli_num_rows($query);
    
    if($rowCount > 0){
        $fetch = mysqli_fetch_array($query);
        return $fetch[$var2];
    }else{
        return "Invalid member";    
    }
}    

---

Variables declared inside functions have function scope. You need to prefix them with global to access global variables.

function memInfo() {
    global $dbc;
}

Alternatively, you can pass-in the variable as a parameter of the function.

---

Your $dbc variable inside function memInfo is considered as "function scope" variable. If you need to use the global instance (previously defined $dbc = mysqli_ blah blah...) you need to declare as "global scope" inside your function. Like this:

function memInfo($var1, $var2){
    global $dbc;
    var_dump($dbc);
    $query = mysqli_query($dbc, "SELECT * FROM `members` WHERE id = '".$var1."'")or die(mysqli_error($dbc));
    $rowCount = mysqli_num_rows($query);

    if($rowCount > 0){
        $fetch = mysqli_fetch_array($query);
        return $fetch[$var2];
    }else{
        return "Invalid member";    
    }
}

More on this subject in php manual:

http://php.net/language.variables.scope.php