Ingesting a big CSV file, one line at a time...

read.php

#!/usr/bin/env php
<?php
/**
 * Either make this file executable with `chmod +x read.php` or
 * run with `php read.php` passing the input file as the first
 * argument, e.g. `php read.php data.csv` or `read.php data.csv`.
 * If the file contains a header row, add an environment variable,
 * like so: `CSV_HEADER_ROW=1 php read.php data.csv`
 */

$file = fopen($argv[1], 'r');

$fields = ( isset($_SERVER['CSV_HEADER_ROW']) ?
    fgetscsv($file) : null
);

while ( $values = fgetcsv($file) )
{
    if ( $fields ) $values = array_combine($fields, $values);

    // Do something with the $values...
}

fclose($file);