自定义“Markdown”式标签

Question

I want to create custom tags for different things like bold, underline and italic without using a Markdown library/class.

For example

*Bold text*
/Italic text/
_Underlined text_

So the above would be changed to:

<strong>Bold text</strong>
<em>Italic text</em>
<u>Underlined text</u>

I have no idea where to begin and have been searching for a solution for ages.

I read a few tutorials on regular expressions but still unsure how to approach this.

Thanks in advanced.

Answer 1

Here is a recursive function to do that with regex. The tricky part (for me) was the use of forward slash / which is also used in the close tags. So at first i insert {} and replaces those with / in the very end.

test text :

$input ="
*Bold text*
bla bla bla
/Italic text/
bla bla bla
_Underlined text_
bla bla bla
";

replace function :

function markdown(&$text, $code, $tag, $open) {
    if (strpos($text, $code)) {
        $insertTag=($open) ? '<'.$tag.'>' : '<{}'.$tag.'>';
        $reg='['.preg_quote($code).']';
        $text=preg_replace($reg, $insertTag, $text, 1);
        markdown($text, $code, $tag, !$open);
    } else {
        return;
    }
}

run :

markdown($input, '*', 'strong', true);
markdown($input, '/', 'em', true);
markdown($input, '_', 'u', true);
$input=str_replace('{}', '/', $input);
echo $input;

outputs :

<strong>Bold text</strong>
bla bla bla
<em>Italic text</em>
bla bla bla
<u>Underlined text</u>
bla bla bla