Text replacement: PHP/regex

Question

I am presented with an HTML document similar to this in view source mode (the below is simplified for brevity):

Answer 1

I was about to post an answer on your next question but Casimir closed it before I got the chance. I am coming back here to post a proper html parse-then-replace technique for the benefit of researchers and you.

Code: (Demo)

define('LOOKUP', [
    'block' => [
        'welcome-intro'         => 'custom intro'
    ],
    'variable' => [
        'contact-email-address' => 'mmu@mmu.com',
        'system_version'        => 'sys ver',
        'system_name'           => 'sys name',
        'system_login'          => 'sys login',
        'activate_url'          => 'some url'
    ],

]);

$dom = new DOMDocument();
libxml_use_internal_errors(true);
$dom->loadHTML($html);
$xpath = new DOMXpath($dom);

foreach ($xpath->query("//*[not(self::textarea or self::select or self::input) and contains(., '{{{')]/text()") as $node) {
    $node->nodeValue = preg_replace_callback('~{{{([^:]+):([^}]+)}}}~', function($m) {
            return LOOKUP[$m[1]][$m[2]] ?? '**unknown variable**';
        },
        $node->nodeValue);
}
echo $dom->saveHTML();

Output:

    

            

                

                    custom intro
                
            
        
    

            

                

                                        
You are using system version: sys ver
                    
Your address: mmu@mmu.com
                    

                                                                                    

                            

                        
                    
Personal information

                    

                        Name * 

                    
                
Enter at least 2 characters and a maximum of 12 characters.

                    

                        Password

                    
                
Your password must be at least 12 characters long, contain 1 special character, 1 nunber, 1 lower case character and 1 upper case character.
Biographical information

                    

                        Biography
                A minimum of 40 characters and a maximum of 255 is allowed. This hint is displayed inline.
                    
                {{{variable:system_name}}}

{{{variable:system_login}}}

                    

                        Interests
                A minimum of 40 characters is required. This hint is displayed inline.
                    
                <p>sys name<br></p><p>sys login</p><p>some url<br></p>
Submit
        
                
            
        
    

There aren't too many tricks involved.

1. Parse the HTML with DOMDocument and write a filtering query with XPath which requires nodes to not be textarea|select|input tags and they must contain {{{ in their text. There will be several "magical" ways to filter the dom -- this is just one way that feels efficient/direct to me.

2. I use preg_replace_callback() to perform replacements based on a lookup array.

3. To avoid use() in the callback syntax, I make the lookup available inside the callback's scope by declaring it as a constant (I can't imagine you need it to be a variable anyhow).

4. I found during testing that DOMDocument didn't like the

   tags, so I silenced the complaints with libxml_use_internal_errors(true);.