Bob's Blog

In the previous article, I said that implode() only works on simple, numeric arrays, but what if you want to do something similar with an associative array of keys and values. You can create a new array that implode() will like and run impolde() on that array. In this article we'll see how.

Let's take this array from the previous article:

$nameArray = array(
  'BobRay' => 'bobray@somewhere.com',
  'JohnDoe' => 'johndoe@gmail.com',
  'JaneRoe' => 'janeroe@aol.com',
);

We want to print a line of text to display the results like this:

The values are: BobRay (bobray@somewhere.com), JohnDoe (johndoe@gmail.com), JaneRoe (janeroe@aol.com)

We can't call implode() directly on the associative array, but we can create a new simple numeric array that will give us what we want when we use implode() on it.

The Code

Here's our snippet. Notice that at the top of the snippet we've included the array of names we showed above, though it could just as well have come from somewhere else.

$output = '';

$nameArray = array(
  'BobRay' => 'bobray@somewhere.com',
  'JohnDoe' => 'johndoe@gmail.com',
  'JaneRoe' => 'janeroe@aol.com',
);

/* Create the new array */
$users = Array();

/* Add each user to the new array */
foreach ($nameArray as $key => $value) {
  $users[] = $key  . ' (' . $value . ')';
}
$output =  'The values are: '. implode(', ',$users);
return $output;

Because of the way PHP handles variable in double quotes, we could also use this line inside the foreach() loop:

$users[] = "$key ($value)";

The $key and $value variables will be replaced, the space and the two parentheses will be left as is. Which method you use is a matter of personal preference.

It's possible to do this in a custom function using a combination of array_map(), array_keys(), and array_values(), but I consider it ugly, inefficient, and difficult to read. It also depends on the version of PHP. For the curious, here it is:

$array = Array(
  'foo' => 5,
  'bar' => 12,
  'baz' => 8
);

// pre PHP 5.3:
$output =  'The values are: '. implode(', ', array_map(
   create_function('$k,$v', 'return "$k ($v)";'),
   array_keys($array),
   array_values($array)
));

// PHP 5.3+:
$output =  'The values are: '. implode(', ', array_map(
   function ($k, $v) { return "$k ($v)"; },
   array_keys($array),
   array_values($array)
));

return $output;

Here is a another interesting version offered up by Jason Coward (OpenGeek), using array_walk and a PHP closure. It also requires PHP 5.3 and my research suggests that it will be slightly slower than the original iterator version at the top of this article, though I haven't run any benchmarks myself.

$array = array(
    'key1' => 'value1',
    'key2' => 'value2',
    'key3' => 'value3',
);
$flattened = $array;
array_walk($flattened, function(&$value, $key) {
    $value = "{$key} ({$value})";
});
echo 'The values are ' . implode(', ', $flattened);