Question

I am dealing with a textarea user input which some characters are reserved for example:

[ means <h1>
] means </h1>
{ means <p>
} means </p>

Example user input:

[Hello World title]
{hello worlds paragraph
and paragraph continues after line break}

Example system display:

<h1>Hello World title<h1>
<p>hello worlds paragraph<br/>
and paragraph continues after line break</p>

---

All the HTML tags are filtered out from user input, and PHP script will replace these characters for the front-end.

I want to use PHP function “nl2br” to replace line breaks with <br/>.

The problem is only the line breaks between { and } characters should be replaced by <br />.

Also I need to consider if user input more than one paragraph using {}.

Answer 1

I’d do both replacements at the same time, using preg_replace_callback:

<?php

$input="{user input
user input}

newlines that aren't replaced";

function format_paragraph($m){
    return '<p>'.nl2br($m[1]).'</p>';
}

echo preg_replace_callback("/\{(.*)\}/s",format_paragraph,$input);

?>

Test the code here

This example will add both the p tags and replace newlines with
in one single replacement.