Iterate array in Object from Class using fetch(PDO::FETCH_ASSOC) - php

Question

I've a class with viewData() method that pull the data from the DB table.
I want to return the data result array in Class and iterate the array in Object
I'm able to make it work with fetchAll() but couldn't figure it out how to return the result with fetch() using while loop.
<?php
class CrudClass{
private $db;
function __construct($DB_con){
$this->db = $DB_con;
}
/* DATA VIEW METHOD */
public function viewData(){
$sql = "SELECT * FROM tbl_users";
$stmt = $this->db->prepare($sql);
$stmt->execute();
while($row=$stmt->fetch(PDO::FETCH_ASSOC)) {
return $row; // it doesn't work
}
// below code is working
/*if($stmt->rowCount()>0){
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
return $result;
}*/
}
}
// instantiate an Object
$obj = new CrudClass($DB_con);
$rows = $obj->viewData();
foreach($rows as $row) {
echo $row['first_name']. " ". $row['last_name'] ."<br>";
}
?>
The reason I want to do that way, because I don't want to pull the data at one go with fetchAll. Instead want to loop through each row at a time. Any help will be appreciated.

Answer 1

You should return array.
$result = []; // initiate the array
while($row=$stmt->fetch(PDO::FETCH_ASSOC)) {
return $result[] = $row; // put each row in the result array
}
return $result; // return the result array
Now the whole method will look something like below
/* DATA VIEW METHOD */
public function viewData() {
$sql = "SELECT * FROM tbl_users";
$stmt = $this->db->prepare($sql);
$stmt->execute();
$result = []; // initiate the array
while($row=$stmt->fetch(PDO::FETCH_ASSOC)) {
return $result[] = $row; // put each row in the result array
}
return $result; // return the result array
}
This way you are assured that even if there is no result set, only array will get returned.
If above doesn't work. Try following two solutions.
1.Test explicitly for false.
while(($row = $stmt->fetch(PDO::FETCH_ASSOC) !== false) {
return $result[] = $row; // put each row in the result array
}
2.Use foreach
foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
return $result[] = $row; // put each row in the result array
}

Answer 2

It is possible to return something you can use in a foreach without having to preload all the results (i.e. using PDOStatement::fetchAll()) and without returning the PDOStatement itself -- if that's what you are trying to do.
Because PDOStatement implements Traversable you you can construct an IteratorIterator from the PDOStatement and return that.
class CrudClass
{
public function viewData()
{
$sql = "SELECT * FROM tbl_users";
$stmt = $this->db->prepare($sql);
$stmt->execute();
return new \IteratorIterator($stmt);
}
}
// instantiate an Object
$obj = new CrudClass($DB_con);
$rows = $obj->viewData();
foreach($rows as $row) {
echo $row['first_name']. " ". $row['last_name'] ."<br>";
}
Note that if you were try and foreach over $rows more than once, it will error because because the results of a PDOStatement cannot be rewound.