regular expressions

erniegerdie · #1 07-Mar-2004, 19:22

I'm trying to write a function which takes text from a <textarea> submitted in a form, and places lines which are seperated by a new line characters into html paragraphs.

Here's the code.

PHP Code:


<?php
function replaceparagraphs($string) {
    $pattern = "/(.*)(\r|\n)*?\r\n/";
    $replacement = "<p>$1</p>\n";
    return preg_replace($pattern, $replacement, $string);
}

echo replaceparagraphs($_GET['data']);
?>

Example input:
Test data1

Test data2

Test data3

This produces the ouput:
Test data1

Test data2

Test data3

My question is, how do I get the regular expression to remove the second new line chararater?

So the the output produced is:
Test data1
Test data2
Test data3

erniegerdie · #2 08-Mar-2004, 04:25

I found out what the problem was. I had to place a match in (.*) to indicate that I did not want to retrieve the new lines or carriage returns. Done with [^\r\n]. I also had to put in a $ to catch the last string just before the end of the string. Lastly ? was making the preceding match null and void.

New code:

PHP Code:


function replaceparagraphs($string) {
    $pattern = "/(.[^\r\n]*)($|\r|\n)*($|(\r\n))/";
    $replacement = "<p>$1</p>\n";
    return preg_replace($pattern, $replacement, $string);
}

echo replaceparagraphs($_GET['data']);

JdS · #3 08-Mar-2004, 04:46

A few quick questions first... why $_GET['data'], not $_POST['data']?

What is the pattern $pattern = "/(.*)(\r|\n)*?\r\n/"; supposed to match; I looked at it for a while and I still don't get it...

Instead of preg_replace(), I would suggest str_replace() (or even strtr()) to accomplish the same thing... something like this for example:

PHP Code:


<?php
function replaceparagraphs( $string )
{
  $string   = trim( $string );  
  $find     = array( "\r\n\r\n", "\n\n", "\r\r", "\r\n", "\n", "\r", '{NL}' );
  $replace  = array( 
                '</p>{NL}<p>',
                '</p>{NL}<p>',
                '</p>{NL}<p>',
                '<br />{NL}',
                '<br />{NL}',
                '<br />{NL}',
                "\n"
              );
  return( '<p>'.str_replace($find, $replace, $string).'</p>' );
} 
?>

Or... if you don't care much about displaying multiple paragraphs; use nl2br()

erniegerdie · #4 08-Mar-2004, 05:15

No reason why I'm using the $_GET, this is just a test script so far.

The pattern was a bit dodgy, I'm hoping that the pattern in my last post makes more sense. I wanted to use a regular expression, because I wanted some practice in using them.

By the way which way is faster, using the preg_replace or using the str_replace?

cheers

JdS · #5 08-Mar-2004, 05:24

Quote:

Originally Posted by erniegerdie

...The pattern was a bit dodgy, I'm hoping that the pattern in my last post makes more sense. I wanted to use a regular expression, because I wanted some practice in using them....

I understand...

About which is faster; when you can use either; always go with str_replace()...

erniegerdie · #6 08-Mar-2004, 05:34

Quote:

Originally Posted by JdS

always go with str_replace()...

Soz to be a pain, but curious as to why you should always use str_replace()?

JdS · #7 08-Mar-2004, 05:46

Straight from the manual:

Quote:

If you don't need fancy replacing rules, you should always use this function (i.e. str_replace) instead of ereg_replace() or preg_replace().

Besides, I have read many user comments and articles that verify this to be the case...

Like I said, if you can use EITHER, use str_replace(); there are times when you can't use str_replace and then your second choice is obviously preg_replace; I NEVER use ereg_replace, so I don't know...

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