PHP使用while循环来获取项目，使用动态选择功能？

Question

Okay, I've never ever used dynamic functions, not sure why, I've never liked using explode(), implode(), etc.

but I've tried it out, and something went wrong.

    public function fetch($table, array $criteria = null)
    {
        // The query base
        $query = "SELECT * FROM $table";

        // Start checking
        if ($criteria) {
            $query .= ' WHERE ' . implode(' AND ', array_map(function($column) {
                return "$column = ?";
            }, array_keys($criteria)));
        }

        $check = $this->pdo->prepare($query) or die('An error has occurred with the following message:' . $query);
        $check->execute(array_values($criteria));

        $fetch = $check->fetch(PDO::FETCH_ASSOC);

        return $fetch;
    }

This is my query.

Basically I will return the variable $fetch which holds the fetch method.

and then somewhere, where I want to use the while loop to fetch data, I will use that:

$r = new Database();

while ($row = $r->fetch("argonite_servers", array("server_map" => "Wilderness")))
{
    echo $row['server_map'];
}

Now, I am not getting any errors, but the browser is loading and loading forever, and eventually will get stuck due to lack of memory.

That's because the loop is running and running without stopping. Why is it doing this? How can I get this dynamic query to work?

EDIT:

$r = new Database();
$q = $r->fetch("argonite_servers", array("server_map" => "Wilderness"));

while ($row = $q->fetch(PDO::FETCH_ASSOC))
{
    echo $row['server_map'];
}

Answer 1

this is because you call your fetch function in a loop and it re-starts the query every time. You need to call the $check->fetch() in loop instead.

or in other words, if your fetch function (which should probably have a different name) would return $check, then on the returned object you should call fetch() in a loop:

$r = new Database();
$q = $r->fetch(...);
while($q->fetch()){...}

you also need to edit your fetch function to end like this:

    $check->execute(array_values($criteria));
    return $check;
}