为什么db2_fetch_assoc没有始终如一地找到结果?MySQL->DB2 转换

我正在将PHP应用程序从MySQL转换为DB2，IBM_DB2和MySQL PHP扩展之间似乎有一些我无法理解或解决的差异。

如果我在包含 db2_connect() 和 db2_exec() 的函数之外调用记录集，db2_fetch_array()似乎无法从记录集中返回一行，即使返回的记录集存储为对象属性并且在以后调用时仍返回资源 ID 号。

任何人都可以看到为什么对下面的getNextRow()方法的调用无法返回记录集中的下一行吗？ 这在MySQL中工作正常。

class TestClass
{
//Properties
public $result; //Holds the record set returned from a query
public $sql; //Holds the value of the last sql query sent
    function goQuery($sql)
    {
        $this->sql = $sql;
        if($con = db2_connect("MASTER", "DB2USER", "DB2PASSWORD"))
        {
            echo "<li>Connected to master database</li>";   
        }
        if($this->result = db2_exec($con, $sql))
        {
            echo "<li>SQL Query ran successfully</li>"; 
        }
        //Just proving some data can be returned as this point
        $row = db2_fetch_assoc($this->result);
        if(sizeof($row) > 0)
        {
            echo "<li>db2_fetch_assoc returned a record in the resultset (Resource ID: " . $this->result . ") that has " . sizeof($row) . " fields</li>";   
        }
        //Just proving some data can be returned as this point
        $row = $this->getNextRow();
        if(sizeof($row) > 0)
        {
            echo "<li>getNextRow() returned a record in the resultset (Resource ID: " . $this->result . ") the has " . sizeof($row) . " fields</li>";   
        }
    }
    function getNextRow()
    {
        if($row = db2_fetch_assoc($this->result))
        {
            return $row;    
        }
            else
        {
            echo "<li>No results found in " . $this->result . "</li>";  
        }
    }
}
$q = new TestClass();
echo "<h2>Running query TestClass->goQuery()</h2>";
echo "<ul>";
$q->goQuery("SELECT * FROM users");
echo "</ul>";
echo "<h2>Trying to fetch a result using TestClass->getNextRow()</h2>";
echo "<ul>";
$row = $q->getNextRow();
echo "</ul>";

这当前会产生以下输出：

Running query TestClass->goQuery()
Connected to master database
SQL Query ran successfully
db2_fetch_assoc returned a record in the resultset (Resource ID: Resource id #12) that has 25 fields
getNextRow() returned a record in the resultset (Resource ID: Resource id #12) the has 25 fields
Trying to fetch a result using TestClass->getNextRow()
No results found in Resource id #12