Spreadsheets, driven by code.

<?php

require 'vendor/autoload.php';

use \PhpOffice\PhpSpreadsheet\IOFactory;

$spreadsheet = IOFactory::load('inventory.xlsx');
$worksheet = $spreadsheet->getActiveSheet();

// Row 3 of this sheet has no value in column B.
echo 'B3 exists at the start? ' . var_export($worksheet->cellExists('B3'), true) . "\n";

// Only the cells that were actually given a value.
echo "\nIterating existing cells only:\n";

foreach ($worksheet->getRowIterator(2) as $row) {
    $cells = $row->getCellIterator();
    $cells->setIterateOnlyExistingCells(true);

    $line = [];
    foreach ($cells as $cell) {
        $line[] = $cell->getCoordinate() . '=' . var_export($cell->getValue(), true);
    }

    echo '  row ' . $row->getRowIndex() . ': ' . implode('  ', $line) . "\n";
}

echo "\nB3 exists now? " . var_export($worksheet->cellExists('B3'), true) . "\n";

// The default: every cell in the row's range, gaps included.
echo "\nIterating the whole range (the default):\n";

foreach ($worksheet->getRowIterator(2) as $row) {
    $cells = $row->getCellIterator();
    $cells->setIterateOnlyExistingCells(false);

    $line = [];
    foreach ($cells as $cell) {
        $line[] = $cell->getCoordinate() . '=' . var_export($cell->getValue(), true);
    }

    echo '  row ' . $row->getRowIndex() . ': ' . implode('  ', $line) . "\n";
}

// Walking the gaps did not just report them - it created them.
echo "\nB3 exists after the full-range walk? "
    . var_export($worksheet->cellExists('B3'), true) . "\n";

// What an iterator can do that toArray() cannot: stop early.
echo "\nStopping at the first row with qty under 10:\n";

foreach ($worksheet->getRowIterator(2) as $row) {
    $qty = $worksheet->getCell('C' . $row->getRowIndex())->getValue();

    if ($qty < 10) {
        echo '  row ' . $row->getRowIndex() . ' has qty ' . $qty . " - stopping.\n";
        break;
    }

    echo '  row ' . $row->getRowIndex() . " ok.\n";
}