Convert array into csv

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.

Add some improvements based on accepted answer.

1. PHP 7.0 Strict typing
2. PHP 7.0 Type declaration and Return type declaration
3. Enclosure \r, \n, \t
4. Don't enclosure empty string even $encloseAll is TRUE

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

    $delimiter_esc = preg_quote($delimiter, '/');
    $enclosure_esc = preg_quote($enclosure, '/');

    $output = [];
    foreach ($fields as $field) {
        if ($field === null && $nullToMysqlNull) {
            $output[] = 'NULL';
            continue;
        }
        // Enclose fields containing $delimiter, $enclosure or whitespace, newline
        $field = strval($field);
        if (strlen($field) && ($encloseAll || preg_match("/(?:${delimiter_esc}|${enclosure_esc}|\s|\r|\n|\t)/", $field))) {
            $output[] = $enclosure . str_replace($enclosure, $enclosure . $enclosure, $field) . $enclosure;
        } else {
            $output[] = $field;
        }
    }

    return implode($delimiter, $output);

}