While loop and function return with PDO - php

Question

I want to use 'return' function with a while loop for my Mysql query, but it returns only one result.
I have this in my database :
id name author
1 foo fooo
2 foo2 fooo2
It returns only "2", but i want "1","2","3" ect..
Here's my code :
function get_thm_cat() {
require 'database.php';
$req = $bdd->prepare("SELECT * FROM sk_cat ORDER BY id ASC");
$req->execute();
if ($req->rowCount() > 0) {
while ($row = $req->fetch()) {
return '<ul id="ul_cat"><li id="li_cat">'.$row["id"].' Name = '.$row["name"].'<br>';
}
}
$req->closeCursor();
}

Answer 1

With return you stop the execution of the function, which means that when PHP iterates over your loop for the first time and reaches return, it immediately goes back to where you initially called the function. Any subsequent iterations of the while-loop are not executed and your call to $req->closeCursor(); also isn't executed when the result is more than 0 rows because of this.
The easiest way to return multiple strings after each other is to create a temporary variable that you fill up at every iteration and return after the loop, like this:
$output = '';
while ($row = $req->fetch()) {
$output .= '<ul id="ul_cat"><li id="li_cat">'.$row["id"].' Name = '.$row["name"].'<br>';
}
return $output;

Answer 2

return is the command to end the function and continue processing the code where it left off. You should either store the results in the while loop and return the array that holds these results, or you should echo the results in the while loop.
while ($row = $req->fetch_assoc() ) {
echo '<ul id="ul_cat"><li id="li_cat">'.$row["id"].' Name = '.$row["name"].'<br>';
}
or
$results = array();
while ($row = $req->fetch_assoc() ) {
$results[] = '<ul id="ul_cat"><li id="li_cat">'.$row["id"].' Name = '.$row["name"].'<br>';
}
return $results;