Convert array into csv

I'm using the following function for that; it's an adaptation from one of the man entries in the fputscsv comments. And you'll probably want to flatten that array; not sure what happens if you pass in a multi-dimensional one.

/**
  * Formats a line (passed as a fields  array) as CSV and returns the CSV as a string.
  * Adapted from http://us3.php.net/manual/en/function.fputcsv.php#87120
  */
function arrayToCsv( array &$fields, $delimiter = ';', $enclosure = '"', $encloseAll = false, $nullToMysqlNull = false ) {
    $delimiter_esc = preg_quote($delimiter, '/');
    $enclosure_esc = preg_quote($enclosure, '/');

    $output = array();
    foreach ( $fields as $field ) {
        if ($field === null && $nullToMysqlNull) {
            $output[] = 'NULL';
            continue;
        }

        // Enclose fields containing $delimiter, $enclosure or whitespace
        if ( $encloseAll || preg_match( "/(?:${delimiter_esc}|${enclosure_esc}|\s)/", $field ) ) {
            $output[] = $enclosure . str_replace($enclosure, $enclosure . $enclosure, $field) . $enclosure;
        }
        else {
            $output[] = $field;
        }
    }

    return implode( $delimiter, $output );
}

My solution requires the array be formatted differently than provided in the question:

<?
    $data = array(
        array( 'row_1_col_1', 'row_1_col_2', 'row_1_col_3' ),
        array( 'row_2_col_1', 'row_2_col_2', 'row_2_col_3' ),
        array( 'row_3_col_1', 'row_3_col_2', 'row_3_col_3' ),
    );
?>

We define our function:

<?
    function outputCSV($data) {
        $outputBuffer = fopen("php://output", 'w');
        foreach($data as $val) {
            fputcsv($outputBuffer, $val);
        }
        fclose($outputBuffer);
    }
?>

Then we output our data as a CSV:

<?
    $filename = "example";

    header("Content-type: text/csv");
    header("Content-Disposition: attachment; filename={$filename}.csv");
    header("Pragma: no-cache");
    header("Expires: 0");

    outputCSV($data);
?>

I have used this with several projects, and it works well. I should note that the outputCSV code is more clever than I am, so I am sure I am not the original author. Unfortunately I have lost track of where I got it, so I can't give the credit to whom it is due.

A slight adaptation to the solution above by kingjeffrey for when you want to create and echo the CSV within a template (Ie - most frameworks will have output buffering enabled and you are required to set headers etc in controllers.)

// Create Some data
<?php
    $data = array(
        array( 'row_1_col_1', 'row_1_col_2', 'row_1_col_3' ),
        array( 'row_2_col_1', 'row_2_col_2', 'row_2_col_3' ),
        array( 'row_3_col_1', 'row_3_col_2', 'row_3_col_3' ),
    );


// Create a stream opening it with read / write mode
$stream = fopen('data://text/plain,' . "", 'w+');

// Iterate over the data, writting each line to the text stream
foreach ($data as $val) {
    fputcsv($stream, $val);
}

// Rewind the stream
rewind($stream);

// You can now echo it's content
echo stream_get_contents($stream);

// Close the stream 
fclose($stream);

Credit to Kingjeffrey above and also to this blog post where I found the information about creating text streams.

function array_2_csv($array) {
    $csv = array();
    foreach ($array as $item) {
        if (is_array($item)) {
            $csv[] = array_2_csv($item);
        } else {
            $csv[] = $item;
        }
    }
    return implode(',', $csv);
} 

$csv_data = array_2_csv($array);

echo "<pre>";
print_r($csv_data);
echo '</pre>'   ; 

The accepted answer from Paul is great. I've made a small extension to this which is very useful if you have an multidimensional array like this (which is quite common):

Array
(
    [0] => Array
        (
            [a] => "a"
            [b] => "b"
        )

    [1] => Array
        (
            [a] => "a2"
            [b] => "b2"
        )

    [2] => Array
        (
            [a] => "a3"
            [b] => "b3"
        )

    [3] => Array
        (
            [a] => "a4"
            [b] => "b4"
        )

    [4] => Array
        (
            [a] => "a5"
            [b] => "b5"
        )

)

So I just took Paul's function from above:

/**
  * Formats a line (passed as a fields  array) as CSV and returns the CSV as a string.
  * Adapted from http://us3.php.net/manual/en/function.fputcsv.php#87120
  */
function arrayToCsv( array &$fields, $delimiter = ';', $enclosure = '"', $encloseAll = false, $nullToMysqlNull = false ) {
    $delimiter_esc = preg_quote($delimiter, '/');
    $enclosure_esc = preg_quote($enclosure, '/');

    $output = array();
    foreach ( $fields as $field ) {
        if ($field === null && $nullToMysqlNull) {
            $output[] = 'NULL';
            continue;
        }

        // Enclose fields containing $delimiter, $enclosure or whitespace
        if ( $encloseAll || preg_match( "/(?:${delimiter_esc}|${enclosure_esc}|\s)/", $field ) ) {
            $output[] = $enclosure . str_replace($enclosure, $enclosure . $enclosure, $field) . $enclosure;
        }
        else {
            $output[] = $field;
        }
    }

    return implode( $delimiter, $output );
}

And added this:

function a2c($array, $glue = "\n")
{
    $ret = [];
    foreach ($array as $item) {
        $ret[] = arrayToCsv($item);
    }
    return implode($glue, $ret);
}

So you can just call:

$csv = a2c($array);

If you want a special line ending you can use the optional parameter "glue" for this.