在PHP中检测换行符并在输出上调用新段落

So I have this snippet which gets my input from textarea named "cdet" & opens "index.php" & finds string "details" & replace it with my input-

if(ISSET($_REQUEST["sub"])){
    $cdet=$_REQUEST["cdet"];
    $fname = "index.php";

    $fhandle = fopen($fname,"r");
    $content = fread($fhandle,filesize($fname));
    $content = str_replace("details", $cdet, $content);
    $fhandle = fopen($fname,"w");
    fwrite($fhandle,$content); 
}

fclose($fhandle);

& this is the part in "index.php" where the string "details" is-

<p class="wNote">details</p>

What I want is that if a line break/new line occurs in the input, I would end the current

& invoke a new one for the new line...

e.g- if input is

Hello there.. What are you doing here?

then details should be replaced like-

<p class="wNote">Hello there..</p>
<p class="wNote">What are you doing here?</p>

First, you can load file the easier way, with file_get_contents() function:

http://php.net/manual/en/function.file-get-contents.php

Then, after you get that $cdet field value use explode() function to split it by " " sign (new row). That way you'll get an array that contains rows of text.

Then iterate trough that array (with foreach() ) and for every row add that '<p class="wNote">', then row content and then '</p>'.

At end you can't just replace that 'details' words with your result, but you must replace whole '<p class="wNote">details</p>' with your output, because you can have more than one row now.