How to give an error when items are not found in database (PHP and Mysql)

Question

I am newbie in PHP as well as mysql. I'm getting stuck with this problem. What I want is to print an error if the items are not found in the database.

Bellow is my code for it:

$searchParam = '%' . $_GET['q'] . '%';
$moment = microtime(true);
$stmt = $db->prepare('SELECT * FROM product WHERE (serial_number LIKE ? OR name LIKE ?) ORDER BY production_date D$'); //fixed
$stmt->execute(array($searchParam, $searchParam));
$products = $stmt->fetchAll(PDO::FETCH_ASSOC);
$queryTime = microtime(true) - $moment;


$output = array(
        'query_time' => $queryTime,
        'products' => $products
);

die(json_encode($output));

Thank you so much for your help.

Answer 1

I don't know what you exactly want to achieve and if you are parsing the result in the frontend, but this is a simple solution for your case:

$searchParam = '%' . $_GET['q'] . '%';
$moment = microtime(true);
$stmt = $db->prepare('SELECT * FROM product WHERE (serial_number LIKE ? OR name LIKE ?) ORDER BY production_date D$
$stmt->execute(array($searchParam, $searchParam));
$products = $stmt->fetchAll(PDO::FETCH_ASSOC);
$queryTime = microtime(true) - $moment;

if($products) {
    $output = array(
            'query_time' => $queryTime,
            'products' => $products,
            'success' => true
    );
}
else {
    $output = array(
        'query_time' => $queryTime,
        'error' => 'Some error message',
        'success' => false
    );
}

die(json_encode($output));

For a better answer give us some additional info about what you are doing with the response from the php and why it is in json format.

Answer 2

You can simply count the amount of elements returned in the array $products.

if ( count($products) == 0) {
    echo 'No matches found';
}

This all comes after checking if the query succeeded in the first place. If the query fails setting the variables might fail and this if-statement will fail. But this is most likely your solution to checking if no rows have been found on the select statement.

Answer 3

Try this

<?php
$searchParam = '%' . $_GET['q'] . '%';
$moment = microtime(true);
$stmt = $db->prepare('SELECT * FROM product WHERE (serial_number LIKE ? OR name LIKE ?) ORDER BY production_date D$'); //fixed
$stmt->execute(array($searchParam, $searchParam));

$number_of_rows = $stmt->fetchColumn(); 

if($number_of_rows > 0) {
    $products = $stmt->fetchAll(PDO::FETCH_ASSOC);
    $queryTime = microtime(true) - $moment;

    $output = array(
            'query_time' => $queryTime,
            'products' => $products
    );
} else {
    $output = array(
            'query_time' => $queryTime,
            'products' => $products,
            'success' => false,
            'error_msg' =>  'Product not found.',
    );
}
die(json_encode($output));
?>