PHP - PDO not taking imploded array as question ma

问题:

I have a problem with a question mark parameter in a prepared statement using PDO. My Query class looks like this (for now, I'm still adding functionality like data limits, custom parameters filtering and automatic detection of supported statements for the driver being used):

// SQL query
class Query {
    public $attributes;

    // constructor for this object
    public function __construct() {
        if ($arguments = func_get_args()) {
            $tmp = explode(" ", current($arguments));

            if (in_array(mb_strtoupper(current($tmp)), ["ALTER", "DELETE", "DROP", "INSERT", "SELECT", "TRUNCATE", "UPDATE"], true)) {
                // classify the query type
                $this->attributes["type"] = mb_strtoupper(current($tmp));

                // get the query string
                $this->attributes["query"] = current($arguments);

                // get the query parameters
                if (sizeof($arguments) > 1) {
                    $this->attributes["parameters"] = array_map(function ($input) { return (is_array($input) ? implode(",", $input) : $input); }, array_slice($arguments, 1, sizeof($arguments)));
                }

                return $this;
            }
        }
    }
}

This is the code fragment which executes the query:

$parameters = (!empty($this->attributes["queries"][$query]->attributes["parameters"]) ? $this->attributes["queries"][$query]->attributes["parameters"] : null);

if ($query = $this->attributes["link"]->prepare($this->attributes["queries"][$query]->attributes["query"], [\PDO::ATTR_CURSOR => \PDO::CURSOR_FWDONLY])) {
    if ($query->execute((!empty($parameters) ? $parameters : null))) {
        return $query->fetchAll(\PDO::FETCH_ASSOC);
    }
}

And this is how I call it in my test code:

$c1->addQuery("lists/product-range", "SELECT * FROM `oc_product` WHERE `product_id` IN (?);", [28, 29, 30, 46, 47]);

if ($products = $c1->execute("test2")) {
    foreach ($products as $product) {
        print_r($product);
    }
}

The problem I have is I just see the first product (it's a test against a vanilla OpenCart installation) with id 28. As you can see in my code, if the passed parameter is an array, it gets automatically detected by the lambda I have in place in the Query class constructor, so it gets rendered as a string like 28,29,30,46,47.

Is there a missing parameter in PDO setup I'm missing? Or maybe there's some bug or platform limit in what I'm doing? I know there's some limitations on what PDO can do in regards to arrays, and that's why I pre-implode all arrays for them to be passed like a simple string.

There's some procedures I've seen here in SO which, basically, composes the query string like WHERE product_id IN ({$marks}), where $marks is being dynamically generated using a procedure like str_repeat("?", sizeof($parameters)) but that's not what I'm looking for (I could resort to that in case there's no known alternative, but it doesn't look like a very elegant solution).

My development environment is composed of: Windows 7 x64, PHP 5.4.13 (x86, thread-safe), Apache 2.4.4 (x86) and MySQL 5.6.10 x64.

Any hint would be greatly appreciated :)

回答1:

A ? placeholder can only substitute for a single literal. If you want an IN clause to accept an arbitrary number of values, you must prepare a new query for each possible length of your array.

E.g., if you want to select ids in array [1, 2], you need a query that looks like SELECT * FROM tbl WHERE id IN (?,?). If you then pass in a three-item array, you need to prepare a query like SELECT * FROM tbl WHERE id IN (?,?,?), and so on.

In other words, you cannot know with certainty what query you want to build/create until the moment you have the data you want to bind to the prepared statement.

This is not a PDO limitation, it is fundamental to how prepared queries work in SQL databases. Think about it--what datatype would the ? be in SQL-land if you said IN ? but had ? stand in for something non-scalar?

Some databases have array-types (such as PostgreSQL). Maybe they can interpret IN <array-type> the same way as IN (?,?,...) and this would work. But PDO has no way of sending or receiving array-type data (there is no PDO::PARAM_ARRAY), and since this is an uncommon and esoteric feature it's unlikely PDO ever will.

Note there is an extra layer of brokenness here. A normal database, when faced with the condition int_id = '1,2,3,4' would not match anything since '1,2,3,4' cannot be coerced to an integer. MySQL, however, will convert this to the integer 1! This is why your query:

$pstmt = $db->prepare('SELECT * FROM `oc_product` WHERE `product_id` IN (?)');
$pstmt->execute(array('28,29,30,46,47'));

Will match product_id = 28. Behold the insanity:

mysql> SELECT CAST('28,29,30,46,47' AS SIGNED INTEGER);
+------------------------------------------+
| CAST('28,29,30,46,47' AS SIGNED INTEGER) |
+------------------------------------------+
| 28                                       |
+------------------------------------------+
1 rows in set (0.02 sec)

回答2:

Lambda detects an array and creates coma delimited string from it, and passed argument is treated as string, so the query looks like:

SELECT * FROM tbl WHERE id IN('1,2,3,4')

'1,2,3,4' is one string value for SQL.

If you are expecting only numerical values, you can omit adding them as parameters and simply put them in the query:

$a = [28, 29, 30, 46, 47];
$s = "SELECT * FROM tbl WHERE id IN(".implode(',', array_map('intval', $a)).")";

For different data types, you have to add as many parameter placeholders as you need, and bind every parameter separately.