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Re: How do I do this search and replace? [message #172347 is a reply to message #172304]

Mon, 14 February 2011 09:14

Erwin Moller
Messages: 228
Registered: September 2010

Karma:

Senior Member

On 2/12/2011 11:51 PM, BootNic wrote:
> On Sat, 12 Feb 2011 13:15:44 -0800 (PST)
> "laredotornado(at)zipmail(dot)com"<laredotornado(at)zipmail(dot)com> wrote:
>
>> I'm using PHP 5. I want to search for all instances of the "\n"
>> character in my $contents variable and replace it with "\r\n".
>> However, I do not want to replace the "\n" if the character
>> immediately before is already a "\r". How would I construct such
>> a search and replace to do this?
>
> http://www.regular-expressions.info/lookaround.html#lookbehind
>
> using negative lookbehind
>
> $contents = preg_replace("/(?<!\r)\n/", "\r\n", $contents);
>
>

One addition: Using the double replacement strategy as described by
Richard is easier to understand (for non-regexp people), but needs 2
sweeps over the content.

In case performance matters (more specifically: if the $contents is a
huge string, or/and you have to do this replacement many times
sequentially), if might be better to use the above approach from
BootNic, because I expect it will be much faster.

If performance isn't an issue, pick whatever suits you. :-)

Regards,
Erwin Moller

--
"That which can be asserted without evidence, can be dismissed without
evidence."
-- Christopher Hitchens

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[Message index]

		How do I do this search and replace? By: laredotornado@zipmail on Sat, 12 February 2011 21:15
		Re: How do I do this search and replace? By: richard on Sat, 12 February 2011 21:20
		Re: How do I do this search and replace? By: Evan Platt on Sat, 12 February 2011 22:09
		Re: How do I do this search and replace? By: sheldonlg on Sat, 12 February 2011 23:59
		Re: How do I do this search and replace? By: Tim Streater on Sun, 13 February 2011 00:08
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 00:24
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 00:40
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 01:03
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 00:58
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 00:57
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:14
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 01:23
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:29
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 01:38
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 01:54
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:00
		Re: How do I do this search and replace? By: spambait on Sun, 13 February 2011 13:16
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 13:33
		Re: How do I do this search and replace? By: me on Sun, 13 February 2011 13:45
		Re: How do I do this search and replace? By: sheldonlg on Sun, 13 February 2011 13:48
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:51
		Re: How do I do this search and replace? By: spambait on Mon, 14 February 2011 01:58
		Re: How do I do this search and replace? By: Denis McMahon on Mon, 14 February 2011 02:25
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:51
		Re: How do I do this search and replace? By: sheldonlg on Mon, 14 February 2011 12:50
		Re: How do I do this search and replace? By: Jerry Stuckle on Mon, 14 February 2011 12:58
		Re: How do I do this search and replace? By: Denis McMahon on Mon, 14 February 2011 15:34
		Re: How do I do this search and replace? By: Jerry Stuckle on Mon, 14 February 2011 17:57
		Re: How do I do this search and replace? By: spambait on Sun, 13 February 2011 01:48
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:01
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:05
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:13
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:33
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:44
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 02:49
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 02:53
		Re: How do I do this search and replace? By: me on Sun, 13 February 2011 13:32
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 13:37
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:53
		Re: How do I do this search and replace? By: Denis McMahon on Sun, 13 February 2011 04:16
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 04:34
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 04:50
		Re: How do I do this search and replace? By: richard on Sun, 13 February 2011 05:35
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 06:11
		Re: How do I do this search and replace? By: sheldonlg on Sun, 13 February 2011 13:19
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 13:56
		Re: How do I do this search and replace? By: Evan Platt on Sun, 13 February 2011 15:09
		Re: How do I do this search and replace? By: Jerry Stuckle on Sun, 13 February 2011 15:19
		Re: How do I do this search and replace? By: Denis McMahon on Sat, 12 February 2011 22:03
		Re: How do I do this search and replace? By: BootNic on Sat, 12 February 2011 22:51
		Re: How do I do this search and replace? By: The Natural Philosoph on Sun, 13 February 2011 00:21
		Re: How do I do this search and replace? By: Curtis Dyer on Mon, 14 February 2011 09:01
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:54
		Re: How do I do this search and replace? By: Erwin Moller on Mon, 14 February 2011 09:14
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 09:55
		Re: How do I do this search and replace? By: Erwin Moller on Mon, 14 February 2011 10:04
		Re: How do I do this search and replace? By: The Natural Philosoph on Mon, 14 February 2011 10:28
		Re: How do I do this search and replace? By: Curtis Dyer on Mon, 14 February 2011 10:40

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