Best way to perform lite templating in php with regular expression

Question

Hi I'm trying to perform a very easy templating system in PHP.

I wold to do this:

Reading some .md file

Change all {{ variables }} with a corrispondent variable in an array like

$data( array('variable1' => 'value', 
             'variable2' => 'value2'));

Manage the case when a variable doesn't exist, in order to prevent errors like "key not found in array".

Currently I've done this (not in regular expression and also it doens't work)

class Markdown{
    private static $folder = 'markdowns/';

    public static function fill_template($template, $array){

        $text = file_get_contents(self::$folder . $template . '.md'); 
        foreach($array as $key => $value){
            $text = str_replace('{{'.$key.'}}', $value, $text);
        }

        return $text;
    }
}

Any ideas?

Thanks

score 2 · Accepted Answer · answered Apr 05 '18 at 06:43

You can use preg_replace_callback() to transform the pattern {{variable}} to its corresponding value:

public static function fill_template($template, $array){
    $text = file_get_contents(self::$folder . $template . '.md');
    $text = preg_replace_callback('~\{\{([^}]+)\}\}~', function($matches) use ($array) {
        $key = trim($matches[1]); // remove unwanted spaces
        if (isset($array[$key])) return $array[$key]; // return the value if found
        // If not found, return the key:
        return $key;
    }, $text);
    return $text;
}

If the match is not found in the array, the content is returned without {{}}.

Regular expression:

~       # delimiter
\{\{    # two literal { - need to be escaped
(       # start capture group
 [^}]+  # all character until }
)       # end capture group
\}\}    # two literal } - need to be escaped
~       # end delimiter

mleko · Answer 2 · 2018-04-05T06:54:49.080

You can use preg_replace_callback to get simple renderer

function render($template, $vars) {
    return \preg_replace_callback("!{{\s*(?P<key>[a-zA-Z0-9_-]+?)\s*}}!", function($match) use($vars){
        return isset($vars[$match["key"]]) ? $vars[$match["key"]] : $match[0];
    }, $template);
}

Example

echo render(
    "Hello {{ name  }}, how are you today? Date: {{time   }} and it's {{weather}} in {{location}}\n", 
    ["name"=>"World!!", "time"=>date("c")]
);

will render to

Hello World!!, how are you today? Date: 2018-04-05T06:40:34+00:00 and it's {{weather}} in {{location}}

Best way to perform lite templating in php with regular expression

2 Answers2