Setting an Array inside a prepared SQL statement - php

Question

I was told that "There is no way to bind an array to an SQL statement using prepared statements" but I have done it. I am having trouble recreating it though.
I have a statement that updates the database:
if (isset($_POST['printRow'])){
$ids = "";
foreach ($_POST['checkbox'] as $rowid)
{
if(!empty($ids)) $ids .= ',';
$ids .= $rowid;
$_SESSION['ids'] = $ids;
}
}
Here I forgot to post the WORKING code:
$stmt = $conn->prepare("UPDATE just_ink SET deleted=1 WHERE ID IN( " . $ids . ")");
$stmt->execute();
But I still have the following problem:
Where $ids can be either one or multiple ids.
So here is the problem, if I try to take $ids and set a SESSION with it
($_SESSION['ids'] = $ids;)
For use on another page.
On the next page I want to select data using $_SESSION['ids'] so,
$stmt = $conn->prepare("SELECT * FROM just_ink WHERE ID IN( " . $_SESSION['ids'] . ")");
$stmt->execute();
But this doesn't work. Any ideas why?

Answer 1

It doesn't work, because, as you correctly said, you can't bind an array to an SQL statement using prepared statements.
The correct way to bind an array is to create a string of placeholders (question marks) and then bind params in a loop.
Let's say you have an array of necessary ID's called $checkboxes. First, we need to create a string that we will use in our query to bind required params. If $checkboxes has 3 items, our string will look like
$placeholder = "?,?,?";
For this we can use str_repeat function to create a string, where every but last element will add ?, part to placeholder. For last element we need to concatenate single question mark.
$placeholder = str_repeat('?,', count($checkboxes)-1).'?';
Now we need to form and prepare a query that will contain our placeholders:
$query = 'SELECT * FROM just_ink WHERE ID IN (".$placeholder.")';
$stmt = $conn->prepare($query);
To bind every ID to its placeholder we use bindParam method in a loop:
for ($i=0; $i<count($checkboxes); $i++) {
$stmt->bindParam($i+1, ($checkboxes[$i]); #position is 1-indexed
}
$stmt->execute();

Answer 2

You can use arrays with mysqli prepared statements by using call_user_func_array
Your code would end up something like this
$varArray = array();
$questionArray = array();
foreach ($_POST['checkbox'] as $daNumber=>$daValue) {
$questionArray[] = "?";
//We're declaring these as strings, if they were ints, they would be i
$varArray[0] .= 's';
//These must be relational variables. The ampersand is vry important.
$varArray[] = &$_POST['checkbox'][$daNumber];
}
//comma separated series of questionmarks
$allDaQuestions = implode(', ', $questionArray);
$query = "SELECT * FROM just_ink WHERE ID IN ($allDaQuestions)";
$stmt = $conn->prepare($query);
//Where the magic happens
call_user_func_array(array(&$stmt, 'bind_param'), $varArray);
//continue with your regularly scheduled broadcast
$stmt->execute();
//etc.

Answer 3

did you set session_start() at the beginning of the file? you can't use $_SESSION if you don't do that first