Use PDO statement multiple times when using multiple foreach loops - php

Question

I have the following code:
if(!empty($postCountryAdd)) {
$sqlQueryLocalityAdd = $dbh->prepare("SELECT DISTINCT locality_add FROM table WHERE country_add = :country_add ORDER BY locality_add ASC");
$sqlQueryLocalityAdd->execute(array(':country_add' => $postCountryAdd));
echo '<option value="">Select locality</option>';
foreach($sqlQueryLocalityAdd as $localityAddRow) {
//while ($localityAddRow = $sqlQueryLocalityAdd->fetch()){
echo '<option value="';
echo $localityAddRow["locality_add"];
echo '">';
echo $localityAddRow["locality_add"];
echo '</option>';
}
}
If I use foreach($sqlQueryLocalityAdd as $localityAddRow) the code stops responding. Why can't I use foreach more than once? How can I fix it please?

Answer 1

$sqlQueryLocalityAdd is an Object which in this case - which I am showing and OP has used - cannot be iterated through. (bold so #deceze can understand).
You can use the fetchAll() inside a foreach loop to achieve this however.
Your code should look something like this:
[...]
if($sqlQueryLocalityAdd->execute(array(':country_add' => $postCountryAdd)):
foreach($sqlQueryLocalityAdd->fetchAll() as $row):
echo $row['column'];
[...]
endforeach;
endif;
[...]
Difference between an array and an Object

Answer 2

The problem is that the result set can only be iterated once; it is then exhausted, MySQL discards it, and you cannot iterate it again.
I have never actually tried this, but to create a result set which can be iterated several times, you need a scrollable cursor, which you should be able to create thusly:
$sqlQueryLocalityAdd = $dbh->prepare(..., [PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL]);
You should then theoretically be able to iterate the result multiple times.
If that doesn't work, fetch the data into an array using $sqlQueryLocalityAdd->fetchAll() and iterate it as often as you want. In fact, that appears to be the only option with MySQL: https://stackoverflow.com/a/19076778/476

Answer 3

$sqlQueryLocalityAdd isn't a result set, it's a PDOStatement object and you can only iterate over it directly once (as noted clearly by deceze).
The execute() statement returns a boolean true or false on success of the query.
If successfully run, you need to fetch results from it post-query and iterate the array returned:
$success = $sqlQueryLocalityAdd->execute(array(':country_add' => $postCountryAdd));
if($success) {
$results = $sqlQueryLocalityAdd->fetchAll();
foreach($results as $localityAddRow) {
echo '<option value="';
....
The resulting array $results is just a vanilla array, so you can iterate over it as many times as you want.
Note: If the execute() returns false, something is wrong with the query--a successful running query returning a empty result set results will still result in a true.