函数，SQL连接和全局变量

Question

通过在两者之间使用mysql_query和mysql_fetch_array命令调用下面的函数，连接和关闭数据库是否有任何问题

<?php

function dbconnect()
{   
    $sql = "localhost"; 
    $username = "------";
    $password = "-----";
    $connection = mysql_connect($sql, $username, $password) or 
    die("unwable to cct");
    $databse = mysql_select_db("-------", $connection); 
    global $connection;
}

function close()
{
    global $connection;
    mysql_close($connection);
}

dbconnect();
$query = "Some SQL Statement";
$data = mysql_query($query, $connection); - L1
while (mysql_fetch_assoc($data))
{
  //echo something 
}
close();
?>

目前，我收到一个错误消息，说L1的$
connection必须是一种资源，但它是BOOL。如果我在此处给出一条死亡声明，则会触发同样的情况。我不知道怎么了。请找出所有可能的错误。我不得不从编码中休假，过了一会儿我又回来了。

感谢和问候

Answer 1

在 分配变量 之前，
必须使用global关键字。否则，您可以在函数内部声明一个局部变量，然后调用对尚不存在的global的引用。在其他功能中，使用了不存在的全局变量。
__$connection``$connection``$connection

function dbconnect()
{   
    // Global first to be sure the subsequent $connection is the global
    // rather than a new one local to this function
    global $connection;

    $sql = "localhost"; 
    $username = "------";
    $password = "-----";
    // Now this modifies the global $connection
    $connection = mysql_connect($sql, $username, $password) or die("unwable to cct");
    $databse = mysql_select_db("-------", $connection); 
}

更具可读性的是使用$GLOBALS数组：

function dbconnect()
{   
    $sql = "localhost"; 
    $username = "------";
    $password = "-----";

    // Using the $GLOBALS superglobal array
    $GLOBALS['connection'] = mysql_connect($sql, $username, $password) or die("unwable to cct");
    $databse = mysql_select_db("-------", $GLOBALS['connection']); 
}

最好的办法是$connection从dbconnect()其他函数中返回并使用该值：

function dbconnect()
{   
    $sql = "localhost"; 
    $username = "------";
    $password = "-----";
    $connection = mysql_connect($sql, $username, $password) or 
    die("unwable to cct");
    $databse = mysql_select_db("-------", $connection);

    // Return from the function
    return $connection; 
}

// call as 
$connection = dbconnect();
// and define your other functions to accept $connection as a parameter