Help: Problem with prev() and next() with foreach and file statement

Angus

Hi all,

Just a dumb logic error that has me somewhat stumped.

I want to produce a bit of output that shows the words stored in a text file before and after the word im working with.

The text file looks like:

word 1
word 2
word 3
word 4
word 5

The output that I would like should look like:

         word 1 - word 2
word 1 - word 2 - word 3
word 2 - word 3 - word 4
word 3 - word 4 - word 5
word 4 - word 5

Now the code I thought I could use to produce the above was:

<?PHP

$lines = file("keywords.txt");
foreach ($lines as $value)
{

  echo prev($value) . " - ";
  echo $value       . " - ";
  echo next($value) . "<br>";
}

?>

If I comment out the line: echo prev($value) . " - "; then it kinda works.

I have tried multiple combinations of the above code but cant get it to work...

It will work if I use:

 
<?PHP

$lines = file("keywords.txt");
for($i=1;$i<count($lines);$i++)
{
  echo trim($lines[($i-1)]) . " - ";
  echo trim($lines[$i]). " - ";
  echo trim($lines[($i+1)]) . "<br>";
}

?>

But I cant see why the previous wouldnt work using the built in prev() and next() functions to move the variable pointer.

Any ideas 🙂

diego25

Your first code wouldn't work because $lines is a one dimensional array, so $value is one element (i.e. not an array), right? But next() and prev() take an array as argument, so you can't just pass $value.

Diego

Angus

Im new to using text arrays like this so bear with me 🙂

My understanding of the file command as taken from the manual which is why I was using it is:

"file() returns the file in an array. Each element of the array corresponds to a line in the file, with the newline still attached."

So I thought that each line was indeed a value in the array and I thought I could use foreach to process them.

I kind of understand what you are saying - and when I use next($lines) then it get the next value, but prev($lines) seems to kill the lot.

next($value) doesnt work - which makes sense from what you are saying.

Is there an easy way I could "fix" my code?

diego25

I would just use the second code...

Diego