Convert strings such as *italic* to <i>italic</i>, but not if the newline character is within the asterisk limit

Question

I have the following regular expression in my PHP code:

// markers for italic set *Text*
if (substr_count($line, '*')>=2)
{
    $line = preg_replace('#\*{1}(.*?)\*{1}#', '<i></i>', $line);
}

good results.

However, when $line holds <br>, for example

*This is my text<br>* Some other text

Then the regex still considers the text and converts it to:

<i>This is my text<br></i> Some other text

The goal is to not translate the text if <br> is encountered. How do I do this using regular expressions - using what is called "negative lookahead" or how do I change the existing regular expression?

Note: Strings like *This is my text*<br>Some other text<br> and again *italic*<br>END should still be considered and converted.

Idea: Or should I break down the $line and then use a regex to iterate over the result? !

Answer 1

Using the match what you don't want and discard the technique, you can use this regular expression in PHP (PCRE):

\*[^*]*
\*(*SKIP)(*F)|\*([^*]*)\*

and replace it with $1

Regular expression demonstration

PHP code:

$r = preg_replace('/\*[^*]*
\*(*SKIP)(*F)|\*([^*]*)\*/'), 
        "", $input);

illustrate:

• \*:match*
• [^*]*: Matches 0 or more non-* characters
• 
:match

• \*：End of match *
• (*SKIP)(*F): PCRE verb to discard and skip this match
• <代码>|: or
• \*([^*]*)\*: Matches the string enclosed in *
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