str_replace() with arrays: How to capture changes?

sherry

Hello.

I have text that I'm using str_replace() with that looks into an array to see if there's a word match(es) and then makes the appropriate change for each.

What is the most efficient way to compare the original text with the final text and capture all of the editing changes made?

I would think putting str_replace() inside of a loop and going through each element of the array diminishes its efficiency(?).

I'm using PHP5.

Thanks in advance.

bpat1434

I don't know that there's really an easy way to do this. You could easily use [man]strcmp[/man] or [man]strncmp[/man] to tell if the string has been changed (as long as you save the new string to a new variable):

$string = 'This has some bad words darn, cuss, bite which will be replaced by said filtering.';
$filter = array('darn','cuss','bite');
$replace = '--blam!--';
$newString = str_replace($filter, $replace, $string);

if(strcmp($string, $newString) != 0)
    echo 'Words have been changed!!!';

As for counting what's changed, you'd probably want to split each sentence up by spaces, thus chunking it by words. Then use a [man]for[/man] loop to loop through all the words and figure out which ones changed. Continuing from the previous example:

if(strcmp($string, $newString) != 0)
{
    $S_words = explode(" ", $string);
    $n_words = explode(" ", $newString);

if(count($S_words) > count($n_words))
{
    $left = $S_words;
    $right = $n_words;
    $count = count($S_words);
}
else
{
    $left = $n_words;
    $right = $S_words;
    $count = count($n_words);
}

$changed = 0;
for($i=0; $i<$count; $i++)
{
    if(strcmp($left[$i], $right[$i]) == 0)
        continue;

    echo 'The word in spot #' . $i . ' was changed.<br />';
    $changed++;
}
echo 'There were a total of ' . $changed . ' changed words.';
}

Not simple, but it does its job.

sherry

Thanks for your reply, bpat1434.

What I found is that str_replace() has a 4th parameter that provides a count of the number of replacements. It's a cool feature.

Looking at your code, though, you gave me another idea in trying to find the exact words that were replaced:

How about a comparison of lines then for lines that aren't the same, explode them into individual words then maybe use in_array() or something that would provide the necessary results e.g. for each element in array#1, return the element in array#2 in that same indexed position which should be different? Each of these arrays may be 2-dimensional(?).

I'd have to give that a little more thought.

I'm open for more feedback for other ideas.

Thanks again.

bpat1434

Well, if you're going to do that, you may as well use Perl Regular Expressions (preg) functions. So something like:
[man]preg_match_all[/man]('~word|word2|word3|word4~', $subject, $matches);

Then just count $matches to have the number of replacements, and then iterate over it to have what words were/are being replaced.

sherry

Good point, bpat1434.

Thanks for the info.

EDIT: I found the following link:
http://www.phpbuilder.com/board/showthread.php?t=10265207&highlight=preg_match_all+arrays