Transforms a hash table into a CSV. This is useful for dumping results from database queries. Includes an optional row transformer, which can pre-process rows with complex computations (such as decryption).

csv_transform.php

<?php namespace chrisl\utils;

function transform_csv(
    $rows,
    array $cols=[],
    Closure $row_transformer=null,
    array $opts=[
        'skip_header' => false,
        'col_sep' => ',',
        'quote' => '"',
        'escape' => '\\'
        'line_ending' => '\n']) {
    $csv_rows = [];
    if (!$opts['skip_header'])
        $csv_rows[] = $opts['quote'].join($cols, $opts['quote'].$opts['col_sep'].$opts['quote']).$opts['quote'];
    foreach ($rows as $row) { // each result row
        if ($row_transformer) $row = $row_transformer($row, $cols);
        $col_count = count($cols);
        $csv_row = '';
        for ($i = 0; $i < $col_count; ++$i) { // each column
            $col = $cols[$i]; // column name
            $csv_row .= $opts['quote'] .
                str_replace($opts['quote'], $opts['escape'].$opts['quote'], $row[$col]) .
                $opts['quote'];
            if ($i < $col_count - 1)
                $csv_row .= $opts['col_sep'];
        }
        $csv_rows[] = $csv_row;
    }
    return join($csv_rows, $opts['line_ending']) .
        $opts['line_ending'];
}

// Example use case

require 'crypt';
$db = new \mysql('server', 'user', 'pass', 'db');
$crypt = new Crypt();

print transform_csv(
    $db->query('select * from users order by first_name limit 20')->fetch_assoc(), // rows
    [ 'id', 'first_name', 'last_name', 'password' ], // columns (to extract)
    function($row, $cols) { // transform row (optional)
        // decrypt encrypted columns
        $decrypted_row = [];
        $encrypted_cols = array_intersect($cols, ['password']);
        for ($i = 0; $i < count($cols); ++$i) {
            $cell = $row[$cols[$i]];
            if (in_array($cols[$i], $encrypted_cols)) { // column is encrypted
                try { $cell = $crypt->decrypt($cell); }
                catch (CryptException $ex) { $cell = 'ERROR'; }
            }
            $decrypted_row[] = $cell;
        }
        return $decrypted_row;
    }
);