PDO error "Truncated incorrect DOUBLE value" using placeholder - php

Question

I have the following PHP code that works perfectly ($qry_str is actually generated in the PHP):
$qry_str = <<<'QRY'
FIND_IN_SET('6-47', attributes)
AND FIND_IN_SET('4-176', attributes)
AND FIND_IN_SET('9-218', attributes)
QRY;
$pdo->query('DROP TEMPORARY TABLE IF EXISTS `temp_attr`');
$temp_sql = <<<"TEMP"
CREATE TEMPORARY TABLE IF NOT EXISTS `temp_attr` (
SELECT product_id, GROUP_CONCAT(CONCAT(group_id, '-', IF (custom_value != '', custom_value, value_id)) SEPARATOR ',') AS attributes
FROM `products_attributes`
GROUP BY `product_id`
HAVING $qry_str
);
TEMP;
$pdo->query($temp_sql);
$sql = "SELECT
m.recommended_price AS msrp,
m.purchase_price AS cost,
pp.USD AS regular_price,
pc.USD AS special_price,
pc.start_date AS start_date,
pc.end_date AS end_date,
pl.permalink AS permalink,
pi.name AS description,
m.sku AS sku,
m.default_category_id AS cat,
m.id AS prod_id
FROM `products` AS m
LEFT JOIN `products_prices` AS pp ON m.id = pp.product_id
LEFT JOIN `products_campaigns` AS pc ON m.id = pc.product_id
LEFT JOIN `permalinks` AS pl ON (m.id = pl.resource_id AND pl.resource = 'product')
LEFT JOIN `products_info` AS pi ON (m.id = pi.product_id)
LEFT JOIN `products_to_categories` AS ptc ON (m.id = ptc.product_id)
INNER JOIN `temp_attr` AS pa
WHERE ptc.category_id = :cat
AND m.status = 1
AND m.id = pa.product_id
LIMIT 55;
";
$data = $pdo->prepare($sql)
->bindValue('cat', 100)
->execute()
->fetchAll();
However, when I use a placeholder in the temp table code, i.e.
$temp_sql = <<<"TEMP"
CREATE TEMPORARY TABLE IF NOT EXISTS `temp_attr` (
SELECT product_id, GROUP_CONCAT(CONCAT(group_id, '-', IF (custom_value != '', custom_value, value_id)) SEPARATOR ',') AS attributes
FROM `products_attributes`
GROUP BY `product_id`
HAVING :qry_str
);
TEMP;
$sth = $pdo->prepare($temp_sql);
$sth->bindValue('qry_str', $qry_str, PDO::PARAM_STR);
$sth->execute();
I get the following error:
PHP Fatal error: Uncaught PDOException: SQLSTATE[22007]: Invalid datetime format: 1292 Truncated incorrect DOUBLE value: 'FIND_IN_SET('6-47', attributes)
AND FIND_IN_SET('4-176', attributes)
AND FIND_IN_SET('9-218', attributes)
AND FIND_IN_SET(...'
There are no datetime columns in this table.
group_id and value_id are integer columns
Since the code works fine without the placeholder, I'm at a loss as to why the use of a placeholder breaks the code. The placeholder in the main SQL works properly.
PHP 8.0

Answer 1

https://dev.mysql.com/doc/refman/8.0/en/prepare.html explains:
Parameter markers can be used only where data values should appear, not for SQL keywords, identifiers, and so forth.
In your case, you're apparently trying to bind an expression with the FIND_IN_SET() function. You can't do that. All expressions and other SQL syntax must be fixed in the query at the time you prepare it. You can use a parameter only in a place where you would otherwise use a scalar literal value. That is, a quoted string or a numeric literal.