Count Millions of CSV Rows Efficiently in PHP with SplFileObject

This article presents a concise, high‑performance method for counting the number of rows in a CSV file using PHP, even when the file contains millions of lines.

Why use SplFileObject?

SplFileObject reads a file line‑by‑line without loading the whole file into memory, avoiding the huge memory consumption that functions like file_get_contents would cause on large CSVs.

Step‑by‑step implementation

Open the CSV file with SplFileObject:

$file = new SplFileObject('transactions.csv', 'r');

Seek to the maximum possible line index, which moves the internal pointer to the end of the file: $file->seek(PHP_INT_MAX); Retrieve the current zero‑based line number with key() and add one to obtain the total row count:

$rows = $file->key() + 1; // total number of rows

If the CSV includes a header row and you prefer not to count it, simply omit the "+ 1" adjustment.

Result

For a file named transactions.csv that contains 12 lines, the variable $rows will hold the value 12.

This approach provides a short, memory‑efficient way to read and count rows in a CSV file using PHP.