MySQL update multiple rows via PHP - php

Question

I have to update the same value of multiple rows in a table and i would like to avoid multiple mysql_query using a foreach loop that scan every value of an array.
I try to explain using an example.
This is the solution of the problem using a foreach loop
$array=array(1,2,3);
foreach($array as $val){
$sql = "UPDATE mytable SET val_to_update = XX WHERE id = $val";
mysql_query($sql);
}
I didn't like to start hammering database with a crazy number of queries, because the number of element of the array is not fixed, and can also be large.
I have considered using the IN clause of SQL language but without knowing the number of parameters can not seem to find a solution.
Thinked at something like this, but I do not know if it is achievable:
$sql= "UPDATE Illustration SET polyptychID = $id_polyptych WHERE illustrationID IN (?,?,?);
and then bind all the parameters using a foreach loop for scan the array of parameters.
The problem, as I said, is that i don't know the number, so i can't place the right number of ? in sql query and, if I'm not mistaken, the number of occurrences of ? parameters must be the same as the binded parameters.
Anyone have solved a problem like this?

Answer 1

If you are sure, that the array is containing integers, why don't you do it like this:
$array=array(1,2,3);
if (sizeof($array) > 0 {
$sql = "UPDATE mytable SET val_to_update = XX WHERE id IN(".implode(',', $array).")";
mysql_query($sql);
}
If you want to use prepared statement you could create your sql using this code:
$array=array(1,2,3);
if (sizeof($array) > 0 {
$placeholders = array();
for($i=0; $i<sizeof($array); $i++) {
$placeholders[] = '?';
}
$sql = "UPDATE mytable SET val_to_update = XX WHERE id IN(".implode(',', $placeholders).")";
// .....
}
If the values in the $array exists in another table you could use something like this:
$sql = "UPDATE mytable SET val_to_update = XX WHERE id IN (SELECT id FROM another_table WHERE condition = 1)";