PreparedStatement select with php not working as expected - php

Question

I have this query:
SELECT id, result, ip_address, added_date
FROM results
WHERE course_id = (
SELECT id
FROM courses
WHERE course = 'informatica'
AND macro_course_id = (
SELECT id
FROM macro_courses
WHERE macro_course = 'scienze-matematiche-fisiche-e-naturali'
AND organization_id = (
SELECT id
FROM organizations
WHERE organization = 'universita-degli-studi-di-torino'
AND city_id = (
SELECT id
FROM cities
WHERE city = 'torino'
AND region_id = (
SELECT id
FROM regions
WHERE region = 'piemonte' ))))) ORDER BY id DESC
And i'm using this code to do it with a preparedstatement
public function getResults($region, $city, $organization, $macro_course, $course) { //works
//added_date=datetime : YYYY-MM-DD HH:mm:ss
echo "SELECT id, result, ip_address, added_date
FROM results
WHERE course_id = (
SELECT id
FROM courses
WHERE course = '$course'
AND macro_course_id = (
SELECT id
FROM macro_courses
WHERE macro_course = '$macro_course'
AND organization_id = (
SELECT id
FROM organizations
WHERE organization = '$organization'
AND city_id = (
SELECT id
FROM cities
WHERE city = '$city'
AND region_id = (
SELECT id
FROM regions
WHERE region = '$region' ))))) ORDER BY id DESC"; //just for me to know what query is being executed
if ($stmt = $this->mysqli->prepare(("
SELECT id, result, ip_address, added_date
FROM results
WHERE course_id = (
SELECT id
FROM courses
WHERE course = ?
AND macro_course_id = (
SELECT id
FROM macro_courses
WHERE macro_course = ?
AND organization_id = (
SELECT id
FROM organizations
WHERE organization = ?
AND city_id = (
SELECT id
FROM cities
WHERE city = ?
AND region_id = (
SELECT id
FROM regions
WHERE region = ? ))))) ORDER BY id DESC
"))) {
$return = array();
$stmt->bind_param('sssss', $course, $macro_course, $organization, $city, $region);
$stmt->execute();
if ($stmt->fetch()) {
$i = 0;
while ($row = $stmt->fetch()) {
print_r($row);//this is never reached
continue;
$s = new Result($row['result'], $row['added_date'], $row['id']);
$return[$i] = $s;
$i+=1;
}
}
}
return $return;
}
The problem is that this function returns 0 rows and 0 errors (checked with $this->mysqli->error), it seems that $row = $stmt->fetch() is always false.
However, if i copy and execute on PHPMyAdmin the output i get at the function top, i see
Showing lines 0 - 0 ( 1 total, Query time 0.0003 sec)
So the query returns a line but it is not catched by php. What am i missing? How can i fix this?

Answer 1

Because you used $stmt-fetch() two times here
if ($stmt->fetch()) {
$i = 0;
while ($row = $stmt->fetch()) {
Remove the if ($stmt->fetch()) condition, it will work as expected.
EDIT
from docs
Note that all columns must be bound by the application before calling $stmt->fetch().
You have to bind the result before calling $stmt->fetch() like this
/* bind result variables */
$stmt->bind_result($name, $code);