[PHP] 文字列にあるhttpから始まるURLをリンクにする

参考：PHP » autolink() – Seebz Code

<?php
function autolink($str, $attributes=array()) {
  $attrs = '';
  foreach ($attributes as $attribute => $value) {
    $attrs .= " {$attribute}=\"{$value}\"";
  }

  $str = ' ' . $str;
  $str = preg_replace(
    '`([^"=\'>])((http|https|ftp)://[^\s<]+[^\s<\.)])`i',
    '$1<a href="$2"'.$attrs.'>$2</a>',
    $str
  );
  $str = substr($str, 1);

  return $str;
}
?>

EX1

<?php
$str = 'A link : http://example.com/?param=value#anchor.';
$str = autolink($str);

echo $str; // A link : <a href="http://example.com/?param=value#anchor">http://example.com/?param=value#anchor</a>.
?>

EX2

<?php
$str = 'http://example.com/';
$str = autolink($str, array("target"=>"_blank","rel"=>"nofollow"));

echo $str; // <a href="http://example.com/" target="_blank" rel="nofollow">http://example.com/</a>
?>