PHP conditional string replacement

Question

I'm trying to replace the ~ into | between the [ ] in the folowwing case:

{stackoverflow is a [cool~great~fast] website ~ Find your answers [easily~quickly] on stackoverflow}.

Note: The text between the [ ] can be multiline.

I've tried multiple regexs buth with no luck.

My closest call at the moment is:

$text = preg_replace("/\[(.*?)~(.*?)\]/i", "[$1|$2]", $text);

But that returns

{stackoverflow is a [cool~great|fast] website ~ Find your answers [easily|quickly] on stackoverflow}.

You should report which regular expressions you tried. It could be you make a mistake, and the regular expression is not correct. — avpaderno
– avpaderno, Commented Jul 3, 2010 at 22:48

sepp2k · Accepted Answer · 2010-07-03 23:24:05Z

2

You need to use one regex to find all strings in brackets and then another to replace the ~s in them. You can use preg_replace_callback to apply the ~-replacing regex to all the substrings in brackets like this:

preg_replace_callback('/\[[^\]]+\]/', function ($str) {
    return str_replace('~', '|', $str[0]);
}, $my_string)

edited Jul 3, 2010 at 23:24

answered Jul 3, 2010 at 23:00

sepp2k

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2 Comments

tsgrasser Over a year ago

I would use str_replace instead of preg_replace in the callback, as invoking any preg function is fairly costly, so you could use str_replace('~', '|', $str[0]) instead and get the same effect.

sepp2k Over a year ago

@tsgrasser: Fair enough. Done.

user187291 · Accepted Answer · 2010-07-04 00:08:47Z

2

simpler than you think

 echo preg_replace('/~(?=[^\[\]]*\])/s', '|', $a);

?= is a lookahead assertion and reads "followed by". That is, "a tilde followed by some non-brackets and then a closing bracket" - this matches only ~'s inside [ ]

answered Jul 4, 2010 at 0:08

user187291

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1 Comment

sepp2k Over a year ago

This would also replace the ~ in "~la]", i.e. it does not require an opening bracket to occur before the tilde. That's probably not a problem though, so +1.

Billy · Accepted Answer · 2010-07-03 22:46:28Z

0

What are some examples of the regexes you've used? My immediate thought is that [] is tripping you up because that is used to match character classes. If you want to match [ or ] as a literal you must escape it with backslashes: \[ or \].

answered Jul 3, 2010 at 22:46

Billy

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3 Comments

brechtvhb Over a year ago

My closest call was preg_replace("/[(.*?)~(.*?)]/i", "[\1|\2]", $text); But I'm getting a weird character instead of the text.

brechtvhb Over a year ago

the [] are escaped but stackoverflow removes the \ before it for some reason.

sepp2k Over a year ago

@brechtvhb: You get the funny character because \1 and \2 mean different things in double quotes than in single quotes. If I use single quotes and escape the brackets, I get correct results for simple cases with your regex. However it does not work when there are multiple ~s inside the brackets (only the first one in each bracket-pair will be replaced).

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