Delete white space on exact position in php

Question

I was just wondering how I could exactly remove white space or even character by row and position inside row. I can't find info about this but I think that the PHP trim() could help. Also I was thinking about a solution for dynamic text. Where I want do delete all line's which are empty. Or just some of them.

An example:

> here is text blabla
> 
> here is text balabla  balabala
> 
1
2 
3 
> oops too much space
> 
> also here is text

Now how can I strip the 3 white spaces away?

It has to become something like this:

> here is text blabla
> 
> here is text balabla  balabala
> 
> oops too much space
> 
> also here is text

`$text = preg_replace('~(\n|\r\n){3,}~', '\1\1', $text);`? – NullUserException Oct 10 '12 at 08:24 — NullUserException, Oct 10 '12 at 08:24
Are the `>` characters actually there btw? – Ja͢ck Oct 10 '12 at 08:28 — Ja͢ck, Oct 10 '12 at 08:28

Ja͢ck · Accepted Answer · 2012-10-10T09:44:25.933

4

Seems like you want regular expressions then:

preg_replace("#(\r?\n){3,}#", "\n\n", $str);

It replaces 3 newlines or more (i.e. two consecutive empty lines or more) with two newlines (one empty line).

To make sure it works with lines that only seem empty (i.e. a line with only spaces), you need to alter the expression slightly:

preg_replace("#(\r?\n\s*){3,}#", "\\1\\1", $str);

Disclaimer: The \\1\\1 idea came from NullPointerException :)

You can also take a different route and solve it iteratively:

// $final is the result of the operation
// $n keeps track of how many empty lines were seen
$final = ''; $n = 0;
// $str is the original content, we split it into separate lines
foreach (preg_split("/\r?\n/", $str) as $line) {
        if (strlen(trim($line))) {
                $n = 0;
        } elseif (++$n >= 2) {
                continue;
        }
        // append to the final result
        $final .= "$line\n";
}
// rtrim($final, "\n");

Turns out that using explode() in the above iterative solution improves the performance; it still works with space-only lines because of trim(). However, you need to trim the newlines on the right side using rtrim($final, "\n");.

edited Oct 10 '12 at 09:44

answered Oct 10 '12 at 08:26

Ja͢ck

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@NullUserException Haha figured you'd see that lol. I was distracted while I wrote the first pass. – Ja͢ck Oct 10 '12 at 08:30
can we haz an speedtest about what is faster? – EaterOfCode Oct 10 '12 at 08:51
@Jack I just did wrote a speedtest http://codepad.viper-7.com/o9jAch mine is faster on codepad but yours is faster on my WAMP :O – EaterOfCode Oct 10 '12 at 09:28
@EaterOfCorpses The difference is mainly due to `explode()` vs `preg_replace()`. Both our iterative solutions don't return the same result as the `preg_replace()` though; yours adds a newline in front, mine one at the back :) – Ja͢ck Oct 10 '12 at 09:42
Works like a charm, you did it. Stil I am very confused by all the weird parameters inside the usage of preg_replace(). Maby I have to study them more!? – botenvouwer Oct 10 '12 at 09:47
@Jack but why is explode faster on codepad and preg on WAMP :S – EaterOfCode Oct 10 '12 at 09:48

EaterOfCode · Answer 2 · 2012-10-10T09:13:36.270

not regex solution:

 function stripEmptyNewlines($string,$limit = 1){
     $array = explode("\n",$string);
     $emptyLine = 0;
     $newString = "";
     foreach($array as $child){
         if(trim($child) == "") {
             $emptyLine++;
         } else {
             $emptyLine = 0;
         }
         if($emptyLine < $limit + 1){
             $newString .= "\n" . $child;
         }
     }
     return $newString;
 }

score -1 · Answer 3 · answered Oct 10 '12 at 08:25

-1

use the ReadLine() method on your text.

if ReadLine().Trim() != "", then add it to the output string. (else it will be an empty line)

answered Oct 10 '12 at 08:25

voluminat0

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@EaterOfCorpses its c# no php :) p.s. it=ans – Prasanth Oct 10 '12 at 08:41
This function you call readline is part of the gnu extension and is used for building a command line. – botenvouwer Oct 10 '12 at 09:42

Delete white space on exact position in php

An example:

3 Answers3