This post goes over how to read a CSV file with PHP without external dependencies.

Prerequisites

Given a CSV file file.csv:

id,name
1,John
2,Mary

Get CSV

PHP function that opens and gets the CSV file:

// main.php
function readCSV(string $csv): array
{
    $file = fopen($csv, 'r');
    $rows = [];

    while (!feof($file)) {
        $rows[] = fgetcsv($file);
    }

    fclose($file);
    $rows = array_filter($rows);

    return $rows;
}

print_r(readCSV('file.csv'));

Running the script in a command-line:

php main.php

Output:

Array
(
    [0] => Array
        (
            [0] => id
            [1] => name
        )

    [1] => Array
        (
            [0] => 1
            [1] => John
        )

    [2] => Array
        (
            [0] => 2
            [1] => Mary
        )

)

Transform CSV

PHP function that opens, gets, and transforms the CSV file:

// main.php
function readCSV(string $csv): array
{
    $file = fopen($csv, 'r');
    $rows = [];

    while (!feof($file)) {
        $rows[] = fgetcsv($file);
    }

    fclose($file);
    $rows = array_filter($rows);

    $output = [];
    $headers = array_shift($rows);

    foreach ($rows as $row) {
        $transform = [];

        foreach ($headers as $index => $header) {
            $transform[$header] = $row[$index];
        }

        $output[] = $transform;
    }

    return $output;
}

print_r(readCSV('file.csv'));

Running the script in a command-line:

php main.php

Output:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => John
        )

    [1] => Array
        (
            [id] => 2
            [name] => Mary
        )

)

Demo

Replit: