strrpos wont evaluate certain strings

Question

$target is a char and I am trying to find the last occurrence of that char in $line. I get -1 for every single output even if I am certain the $target does exist within $line at some index.

    $fh = fopen($someFile, "r");
    while (!feof($fh)) {
    $test = fgets($fh);
    $words = explode(",", $test);
    $line = $words[0];
    $target = $words[1];

    $answer = strrpos($line, $target);

    if ($answer !== false) {
    echo $answer;
    }
    else echo -1;
    echo "\n";
    }

This code returns -1 for every single value. If I change the $line to $test in the strrpos function it can find the index every time. I checked $line to make sure it is not empty and it is in fact the first part of the string. Why doesn't this work?

@MarcoS Well, if he forgets to actually do that, he wil indeed always get -1 — nl-x, Jul 10 '14 at 07:32
Well, not even -1, strrpos returns FALSE if no match is found... — MarcoS, Jul 10 '14 at 07:53
@MarcoS he will always get -1, because his simply states `else echo -1;` with an `if()` that will never be true. — nl-x, Jul 10 '14 at 07:54
Yes: he (she?) will get "-1" in output, since he did not correctly assign $answer. But, after assigning it, he will have to check for `$answer !== FALSE`, to get a reasonable result... :-) — MarcoS, Jul 10 '14 at 08:05

MarcoS · Answer 1 · 2014-07-12T09:11:30.507

I don't know if I did correctly understand your answer... However, you have some errors, in your code:

1) you did not assign the result of strrpos to $answer (probably just a typo...).
2) you did test function result for -1, but that function returns FALSE if no match is found.

This should work:

<?php
  $someFile = "data";
  $fh = fopen($someFile, "r");
  while (!feof($fh)) {
    $test = fgets($fh);
    $words = explode(",", $test);
    $line = $words[0];
    $target = $words[1];

    $answer = strrpos($line, $target);
    if ($answer !== FALSE) {
      echo $answer;
    } else {
      echo -1;
    }
    echo "\n";
  }
?>

With this data file:

haystack,stack,

this code prints:

which is supposedly the answer you're looking for...

Before going to production (:-) you should also be aware that:

feof() should be checked after fgets(), not before...
always use chop() on fgets()'s, to avoid newline issues (fgets return the newline, too...)

UPDATE
To better reflect your use case (I hope), and to implement all advises I wrote in the comments, here is an updated version of workinkg code. Please post your data if still should be not working for you...

File "test.php":

<?php
  $someFile = "data";
  $fh = fopen($someFile, "r");
  while (1) {
    $test = fgets($fh);
    if (feof($fh)) break;
    $test = chop($test);
    $words = explode(",", $test);
    $line = $words[0];
    $target = $words[1];

    $answer = strrpos($line, $target);
    if ($answer !== FALSE) {
      echo $answer;
    } else {
      echo -1;
    }
    echo "\n";
  }
?>

File "data":

haystack,s

run:

$ php test.php
3

Thank you for excusing my typo and for the extra advice. In the process of converting some Java puzzle solutions to PHP and gain more practice. I STILL get -1 for every answer with this exact code, even if I know the $target exists in $line. $target is a single character and I am trying to find the last occurrence of that char in $line if that info helps. I really don't understand why it won't pick up the first if clause. — STLCards77, Jul 10 '14 at 20:25

score 0 · Answer 2 · answered Jul 10 '14 at 07:51

It is unclear what you are asking. Explode does not put the second element inside the first one, like you are suggesting in your question. Also in your question you evaluate $answer in your if(), but you don't set $answer anywhere in the code you show us.

But just to clarify:

$string = "abcd,efghij,kl";
$array = explode(",",$string);
echo $array[0]; // abcd
echo $array[1]; // efghij
echo $array[2]; // kl

If you need to know how big any of the elements are, or when the next elements start, just use strlen():

echo strleng($array[0]); // 4
echo strleng($array[1]); // 6
echo strleng($array[2]); // 2

As $array[0] is 4 characters long, and we have a comma after it, $array[1] starts at index 4+1 = 5.

And $array[2] starts at index 12 because the first 2 elements with the 2 commas are 4+1+6+1 = 12.

strrpos wont evaluate certain strings

2 Answers2