On 7/1/05, Richard Lynch <ceo@xxxxxxxxx> wrote:
> On Fri, June 24, 2005 3:18 pm, Dotan Cohen said:
> > I've got a line like this:
> > $str=preg_replace( "-regex here-", '\n<note>\1</note>', $str);
> >
> > Which has one of two problems: If I leave the single quotes around the
> > second argument, then it returns as \n and not a newline. If I change
> > the single quotes to double quotes, then the info from the regex is
> > not inserted in place of the \1.
> >
> > What is one to do in these situations?
>
> Single quotes have only two (2) special characters:
> ' and \
>
> You need \' to get a ' buried inside a single quote.
>
> Since you use \ as the escape character, but you might want \ in the
> string, you also want to use \\ to get a single \ in your string.
>
> That's pretty much *IT* for single quotes.
>
>
> Double quotes have much for flexibility.
>
> Embedded variables, special characters like \n \r \t ..., embedded 1-D
> arrays and object dereferences (->) and even (in recent times) an {}
> construct to evaluate an expression and splice it in.
>
> In PHP, you need \n inside double quotes to get a newline.
> [Okay, there are other ways, but it's the most common way.]
>
> \n inside of single quotes don't mean squat.
>
> So, in PHP "\n" is newline.
>
> I think "\1" just turns into "1" because 1 is not special following "\"...
> But I can't begin to remember *ALL* the characters that are special
> following "\" especially when you start getting into octal/hex
> representations.
>
> The trick to remember is that if you want "\" in PHP, you need "\\" to get
> a single "\"
>
> Now, both PHP *and* RegEx use \ as a special character.
>
> So, not only do you need "\\" in PHP to get a single "\", you *ALSO* may
> need one (or more) \ characters to "feed" into your RegEx.
>
> In your case:
> "\n...\1" turns into this in PHP internally:
> "[newline]...1"
>
> Because \1 don't mean squat to PHP either, really. It just means "1"
>
> [Unless it means ASCII charcter 1, which I doubt...]
>
> Anyway, the \ is being used by PHP as an escape character, and you need a
> \ to get down to the RegEx parser.
>
> "\n...\\1" will do that.
>
> PHP will see the "\\" and turn it into \ internally.
>
> The \ gets handed to the RegEx parser, and it "sees":
> [newline]...\1
> for its input string.
>
> That's what you want.
>
> Always try to "see" your PHP / RegEx strings in three stages:
>
> 1. What you type in PHP.
> 2. What PHP stores internally, which is what it hands to RegEx
> 3. What RegEx is going to "parse" #2 into.
>
> --
> Like Music?
> http://l-i-e.com/artists.htm
>
>
>
Thanks, Richard. I understand now that php doesn't do the regex stuff
itself- it has a module/apple/program called RegEx do the dirty work.
So I have to pay attention to what RegEx will get. Like paying
attention to the source code of html files and not what we see in the
browser.
Thank you for that explanation. I'm just begining to get familiar
enough with php to have the need (and the ability) to understand what
goes on internally.
By the way, I see that you advertise offices on all the planets and
most of the major moons, but when I try to get in contact with the
Uranus branch, I'm told that the nearest operating office is on Earth.
There's 3 planets and over 20 big moons between those planets, why the
gap in coverage?
Dotan Cohen
http://song-lirics.com/sl/index.php
Song Lirics
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