reduce-string.php

<?php

/**
 * Monta string à partir de um array de chave/valor
 */

// rodrigo@blue-wind[~/repositorios/php] $ php reduce.php 
// <a href="http://google.com" id="java" class="php"/>

$a = [
	'href' => 'http://google.com',
	'id' => 'java',
	'class' => 'php'
];

$initialPiece = '<a';
$finalPiece = '/>';
$keys = array_keys($a);
$counter = 0;

$element = array_reduce($a, function($final, $atual) use (&$counter, $keys) {
	$final .= sprintf(' %s="%s"', $keys[$counter], $atual);
	$counter++;
	return $final;
}, $initialPiece);

$element .= $finalPiece;

echo $element . PHP_EOL;