[RESOLVED] Regular expressions help

vaaaska

Trying...to...underestand... :bemused:

I want to strip whitespace and replace it with a hyphen. I can do it with an underscore, but a hyphen causes an error message:

// The input value is 'hello 3'.

$output = preg_replace("/\s/e","-",$input);  // error!
$output = preg_replace("/\s/e","_",$input);  // it works...

Logically speaking I could understand this if the '-' was a shift+ character but it's not - the underscore is. So, I'm completely stumpded as to why this doesn't work.

Oh yes...the error message I receive:

Parse error: parse error in /Library/Apache2/htdocs/test.php(19) : regexp code on line 1

Fatal error: Failed evaluating code: - in /Library/Apache2/htdocs/test.php on line 19

mrhappiness

/\s/ is enough, no need for e, least of all if you don't know what it is used for 🙂

vaaaska

Crap...you are 100% right. It does work that way...of course, I didn't post the entire snip of code...and...you know...sheesh...

I find everything about regex to be a pain...plus, I just can't understand them.

Anyways, I snagged this script from the manual, and apparently there is a reason for the /e to exist. Of course, I don't understand it...

Or, there could be another way to do this...but this approach 'seemed' rather efficient as it's nearly exactly what I need to do.

// remove spaces
$output = preg_replace("/\s/e" , "_" , $input);

// Remove non-word characters
$output = preg_replace("/\W/e" , "" , $output);

Edit...ok, now I get it...totally wrong approach here for what I need. I understand something I guess...

From the manual:
A "word" character is any letter or digit or the underscore character, that is, any character which can be part of a Perl "word". The definition of letters and digits is controlled by PCRE's character tables, and may vary if locale-specific matching is taking place (see "Locale support" above). For example, in the "fr" (French) locale, some character codes greater than 128 are used for accented letters, and these are matched by \w.

Thanks...

vaaaska

Ok, a little backwards thinking (which is a good thing) and this is resolved:

// remove white space
$output = preg_replace("/\s/","_",$input);

// remove non-word characters - hyphens are acceptable to \W
$output = preg_replace("/\W/" , "" , $output);

// change underscores to hyphens
$output = preg_replace("/_/","-",$output);

How are people marking threads resolved?

kburger

vaaaska wrote:
How are people marking threads resolved?

Under the 'Thread Tools' menu at the top of the thread.