Efficient Data Processing with PHP Generators

Modern PHP includes Generators, which let you work with large datasets without using too much memory. Instead of building a huge array and then looping through it, a Generator uses yield to return one item at a time. This keeps only the current value in memory.

Example: Generating Numbers

function getNumbersWithGenerator(int $max): Generator { for ($i = 1; $i <= $max; $i++) { yield $i; } } // Only one number is in memory at once: foreach (getNumbersWithGenerator(1_000_000) as $n) { // Process $n… } 

If you tried to build an array of one million numbers first, PHP would use a lot of memory. With a Generator, it stays small.

Example: Reading a Large CSV File

function readCsvLineByLine(string $filename): Generator { if (!is_readable($filename)) { throw new InvalidArgumentException("Cannot read: $filename"); } $handle = fopen($filename, 'r'); if (!$handle) { throw new RuntimeException("Failed to open: $filename"); } // First row is the header: $header = fgetcsv($handle); while (($row = fgetcsv($handle)) !== false) { yield array_combine($header, $row); } fclose($handle); } // Use it like this: foreach (readCsvLineByLine(__DIR__ . '/large-data.csv') as $record) { // Each $record is an associative array, e.g. ['id'=>'123', 'name'=>'Alice', …] // Process $record without loading the entire file into memory. } 

Because fgetcsv() reads one line at a time and yield returns one row, PHP never loads the whole file at once.

When to Use Generators

• Fetching thousands of database rows: yield each row instead of fetchAll().
• Processing large log files or text files line by line.
• Any situation where you would otherwise build a huge array.

Generators make your PHP code run “lazy”: values are produced on demand. This keeps memory usage low and avoids slowdowns. Next time you need to handle big data in PHP, try a Generator function!