Strict Standards: Only variables should be passed by reference in... - error line

Question

I have error like this:

Strict Standards: Only variables should be passed by reference in /file.php in line 100

In file.php line look like this:

foreach($filelist as $value => $file) {
    // ABOVE LINE IS LINE 100
    if(in_array(end(explode(".", $file)), $extensions)&&is_file($dir.$file)) { $c++; }
    if(IsSet($_GET['start'])) {
        $nav = $_GET['start'];
    } else {
        $nav = "0";
    }
    if(($c > $nav) && ($c < $nav+($pagerows+1))) {
        $link = $dir . $file;
        $hlink = $http . $file;
        $ext = explode(".", $file);
        if(in_array(end($ext), $extensions)&&is_file($link)) {
            $p++;
            if(file_exists($link)) {
                list($width, $height, $type, $attr) = getimagesize($link);
                if($height > SMALL_IMAGE_HEIGHT) {
                    $imageheight = SMALL_IMAGE_HEIGHT;
                } else {
                    $imageheight = $height;
                }

Could you help me? I found topics like this but noon have code like my code.

Hi, I've improved formatting of the question (the comment marking the line 100 wasn't actually visible!) Still, I suggest you to read https://stackoverflow.com/help/mcve and ask questions in accord to this guideline. The nice thing is, once you start to minimize the code that reproduces the problem, it is more likely that you find the source of the problem for yourself. Also, you should site "topics like this" so that we can suggest ones you overlooked. Best regards — YakovL, Apr 28 '18 at 19:41
Possible duplicate of ["Strict Standards: Only variables should be passed by reference" error](https://stackoverflow.com/questions/9848295/strict-standards-only-variables-should-be-passed-by-reference-error) — YakovL, Apr 28 '18 at 19:44

jh1711 · Answer 1 · 2018-04-27T22:52:32.360

0

end accepts its parameter by reference, because it modifies the array. I. e. it moves the array iterator to the last element and returns the last element. That's why you get the warning. You can remove it, if you simply replace the line that produces the error:

if(in_array(end(explode(".", $file)), $extensions)&&is_file($dir.$file)) { $c++; }

Replace with:

$ext = explode(".", $file); 
if(in_array(end($ext), $extensions)&&is_file($dir.$file)) { $c++; }

Like you did in a later part of your code.

Then you could also delete line 105 ($ext = explode(".", $file);), but you don't have to.

edited Apr 27 '18 at 22:52

answered Apr 27 '18 at 21:38

jh1711

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so `if(in_array(end(explode(".", $file)),` change to `if(in_array(end($tmp = explode(".", $file)),` ? – gold1s Apr 27 '18 at 21:45
exactly. Or you could use `$ext`, like you did later in your code. – jh1711 Apr 27 '18 at 21:48
I change to `if(in_array(end($ext = explode(".", $file)), $extensions)&&is_file($dir.$file)) { $c++; }` and error still shown – gold1s Apr 27 '18 at 22:11
My bad. I was sure that the assignment would work like this, but apparently it does not. I'll edit the answer to correct it. – jh1711 Apr 27 '18 at 22:37
The answer should be correct now. Sorry for the confusion. – jh1711 Apr 27 '18 at 22:44
You forgot about ";" but yes, it's works, thank you! – gold1s Apr 27 '18 at 22:51
@gold1s if this answers your question, please don't forget to accept it by clicking the tick on the left – YakovL Apr 28 '18 at 19:43

score 0 · Answer 2 · edited Jun 20 '20 at 09:12

Well you could use something better to get the extension like this

$ext = strrchr($file, ".");

The only difference is this keeps the . so if $file is somefile.txt it return .txt which if you want to get rid of you could always do this

$ext = ltrim(strrchr($file, "."), '.');

For reference

http://php.net/manual/en/function.strrchr.php

strrchr — Find the last occurrence of a character in a string.

string strrchr ( string $haystack , mixed $needle )

This function returns the portion of haystack which starts at the last occurrence of needle and goes until the end of haystack.

So it just finds the last . and return that and everything after, then ltrim is just "left" trim.

P.S. I really dislike using explode for getting the extension, it's one of my pet peeves.

So for your particular case I would:

foreach($filelist as $value => $file) {
    $ext = ltrim(strrchr($file, "."), '.');
    if(in_array($ext, $extensions) && is_file($dir.$file)) { $c++; } 

    if(isset($_GET['start'])) { $nav = $_GET['start']; } else { $nav = "0"; }
    if(($c > $nav)&&($c < $nav+($pagerows+1))) {
    $link = $dir . $file;
    $hlink = $http . $file;
      
    //$ext = explode(".", $file); we've already done this no need to do it again

This way, you get the extension one time, you don't create an array for it explode, you don't move the array pointer to the end of the array end and that's about it.

UPDATE

You can compare these two using microtime to see which is faster, they are both really fast so we have to do about 100k iterations to test it, like this:

$filename = "filename.php";

$start = microtime(true);

for($i=0; $i<=100000; $i++){
    $v=explode(".", $filename);
    $ext1 = end($v);
}

echo "1. ext='$ext1' Complete ".number_format((microtime(true) - $start), 4).PHP_EOL;

$start = microtime(true);

for($i=0; $i<=100000; $i++){
    $ext2 = ltrim(strrchr($filename, '.'), '.');
    
}

echo "2. ext='$ext2' Complete ".number_format((microtime(true) - $start), 4).PHP_EOL;

Outputs

 1. ext='php' Complete 0.0178
 2. ext='php' Complete 0.0098
 ----------------------------
 1. ext='php' Complete 0.0237
 2. ext='php' Complete 0.0125
 ---------------------------
 1. ext='php' Complete 0.0252
 2. ext='php' Complete 0.0098
 ---------------------------
 1. ext='php' Complete 0.0190
 2. ext='php' Complete 0.0102

You can test it here online

One thing is clear, it's almost 2x faster, not that it matters much in this case. But, it never hurts to check these things. Both give equivalent results, but strrchr is easier to read, well if you know what the function does anyway. It's kind of an obscure function but it basically means string right character.

Cheers.

So could you write to me, what should I replace in my code? – gold1s Apr 27 '18 at 22:20 — gold1s, Apr 27 '18 at 22:20

Strict Standards: Only variables should be passed by reference in... - error line

2 Answers2