Since SQLite3Result::numRows is unavailable, use:

<?php
if ($res->numColumns() && $res->columnType(0) != SQLITE3_NULL) {
    // have rows
} else {
    // zero rows
}
?>

Because when there are zero rows:
* SQLite3Result::fetchArray will return '1'
* SQLite3Result::numColumns will return '1'
* Column type for column '0' will be SQLITE3_NULL

According to http://www.php.net/manual/en/sqlite3result.columntype.php, and also per my experience, columnType() doesn't return anything other than SQLITE3_NULL. Consequently, the test suggested in the comment that tries to identify whether a column is NULL is incorrect.

The right thing to do appears to be to test if ($result->fetchArray())[0] == null.

I use the following code to get num_rows:

<?php
...
$nrows = 0;
$result->reset();
while ($result->fetchArray())
    $nrows++;
$result->reset();
return $nrows;
...
?>

in response to jan at bootfinder dot co dot uk (comment #115891) about getting num_rows...

how about (not tested)... ?

<?php // do cleans before and after if needed

for ( $nrows = 0; isarray($result->fetchArray()); ++$nrows );
return $nrows;

?>

Here's a snippet that might help you to write a fetchObject function that is also missing:

<?php

function fetchObject($sqlite3result, $objectType = NULL) {
    $array = $sqlite3result->fetchArray();

    if(is_null($objectType)) {
        $object = new stdClass();
    } else {
        // does not call this class' constructor
        $object = unserialize(sprintf('O:%d:"%s":0:{}', strlen($objectType), $objectType));
    }
    
    $reflector = new ReflectionObject($object);
    for($i = 0; $i < $sqlite3result->numColumns(); $i++) {
        $name = $sqlite3result->columnName($i);
        $value = $array[$name];
        
        try {
            $attribute = $reflector->getProperty($name);
            
            $attribute->setAccessible(TRUE);
            $attribute->setValue($object, $value);
        } catch (ReflectionException $e) {
            $object->$name = $value;
        }
    }
    
    return $object;
}

?>

Heavily inspired of Bergmann's Object Freezer :
https://github.com/sebastianbergmann/php-object-freezer/blob/master/Object/Freezer.php