Question

I have this preg_replace patterns and replacements :

$patterns = array(
    "/<br\W*?\/>/",
    "/<strong>/",
    "/<*\/strong>/",
    "/<h1>/",
    "/<*\/h1>/",
    "/<h2>/",
    "/<*\/h2>/",
    "/<em>/",
    "/<*\/em>/",
    '/(?:\<code*\>([^\<]*)\<\/code\>)/',
);
$replacements = array(
    "\n",
    "[b]",
    "[/b]",
    "[h1]",
    "[/h1]",
    "[h2]",
    "[/h2]",
    "[i]",
    "[/i]",
    '[code]***HTML DECODE HERE***[/code]',
);

In my string I want to html_entity_decode the content between these tags :
<code> &lt; $gt; </code> but keep my array structure for preg replace

so this : <code> &lt; &gt; </code> will be this : [code] < > [/code]

Any help will be very appreciated, thanks!

Answer 1

You cannot encode this in the replacement string. As PoloRM suggested, you could use preg_replace_callback specifically for your last replacement instead:

function decode_html($matches)
{
    return '[code]'.html_entity_decode($matches[1]).'[/code]';
}

$str = '<code> &lt; &gt; </code>';
$str = preg_replace_callback('/(?:\<code*\>([^\<]*)\<\/code\>)/', 'decode_html', $str);

Equivalently, using create_function:

$str = preg_replace_callback(
    '/(?:\<code*\>([^\<]*)\<\/code\>)/',
    create_function(
       '$matches',
        'return \'[code]\'.html_entity_decode($matches[1]).\'[/code]\';'
    ),
    $str
);

Or, as of PHP 5.3.0:

$str = preg_replace_callback(
    '/(?:\<code*\>([^\<]*)\<\/code\>)/',
    function ($matches) {
        return '[code]'.html_entity_decode($matches[1]).'[/code]';
    },
    $str
);

But note that in all three cases, your pattern is not really optimal. Firstly, you don’t need to escape those < and > (but that is just for readability). Secondly, your first * allows infinite repetition (or omission) of the letter e. I suppose you wanted to allow attributes. Thirdly, you cannot include other tags within your <code> (because [^<] will not match them). In this case maybe you should go with ungreedy repetition instead (I also changed the delimiter for convenience):

~(?:<code[^>]*>(.*?)</code>)~

As you can already see, this is still far from perfect (in terms of correctly matching the HTML in the first place). Hence, the obligatory reminder: don’t use regex to parse HTML. You will be much better off, using a DOM parser. PHP brings a built-in one, and there is also this very convenient-to-use 3rd-party one.