How do I reverse a set of comma delimited strings and return them in the original order in PHP?

Question

This is the code I have so far. I just started learning PHP today and I'm not sure why my code isn't working.

<?php

function backwards($input)
{
    $str = $input;
    $revStr = "";
    $str = explode(",",$str);
    for($x = 0; $x < strlen($str); $x++){
        $revStr .= strrev($str[$x]);
    }
    return $revStr;
}

Any help would be greatly appreciated!

edit: Here is an example input

Php,Arrays,Mysql

here is what i would like the output to be:

phP,syarrA,lqsyM

edit2:

Figured it out. Made a few minor edits. Not sure if it's the most efficient code but it works.

<?php

function backwards($input)
{
    $str = $input;
    $revStr = "";
    $str = explode(",",$str);
    for($x = 0; $x < count($str); $x++){
        if($x == count($str) - 1){
            $revStr .= strrev($str[$x]);
        }
        else{
            $revStr .= strrev($str[$x]) . ",";
        }
    }
    return $revStr;
}

`strlen()` return the length of string, what you pass inside is an array, what you want is `count()` — , Mar 13 '19 at 04:40
I have added the answer on the basis of provided link, Please check. — Ankur Tiwari, Mar 13 '19 at 04:57
[Why can't I mark my title as Solved?](https://meta.stackoverflow.com/questions/311829/why-cant-i-mark-my-title-as-solved) — mario, Mar 13 '19 at 05:11

Andreas · Answer 1 · 2019-03-13T10:31:35.583

Edit, I see you now included an example.
Use array_map and strrev to reverse the words.
Use explode and Implode to make the words array and back to string.

echo implode(",", array_map(function($part){ return strrev($part);},explode(",", $str)));

https://3v4l.org/tr7d6

I believe you should use array_reverse on the exploded string.
Then you can implode it back to a string.
$str = "apple,orange,tomato"; $arr = explode(",", $str); $arr =array_reverse($arr); echo implode(",", $arr); //tomato,orange,apple

https://3v4l.org/Hvd9m

Or, slightly messier but compact:

echo implode(",", array_reverse(explode(",", $str)));

https://3v4l.org/LTu90

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

You are checking the string length of an array inside of your for loop. Also, a custom function is unnecessary, PHP provides us with strrev().

But if you would like to use your own:

function backwards($input)
{
    $str = $input;
    $revStr = "";
    $str = explode(",",$str);
    for($x = 0; $x < count($str); $x++){
        $revStr .= strrev($str[$x]);
    }
    return $revStr;
}

$string = "Php,Arrays,Mysql";
echo backwards($string);

Hope this helps,

score 1 · Answer 3 · answered Mar 13 '19 at 04:43

You need to use count instead of strlen and also need to take reversed string into array and then convert it into string.

You can try this code :

<?php

function backwards($input)
{
    $str = $input;
    $revStr = array();
    $str = explode(",", $str);
    for ($x = 0; $x < count($str); $x++) {
        $revStr[] = strrev($str[$x]);
    }
    return implode(',', $revStr);
}
$str = "Php,Arrays,Mysql";
var_dump(backwards($str));

score 1 · Answer 4 · edited Mar 13 '19 at 04:47

1

use $str[0] in for loop syntax.

like this => for($x = 0; $x < strlen($str[0]); $x++)

edited Mar 13 '19 at 04:47

Ankur Tiwari

2,762
2
23
40

answered Mar 13 '19 at 04:45

Vikal Singh

84
1
2
10

1

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value.[Read this](https://stackoverflow.com/help/how-to-answer). – Shanteshwar Inde Mar 13 '19 at 04:50

score 1 · Answer 5 · answered Mar 13 '19 at 04:47

Just some modification and you got your desired output. You can use explode and implode function of php with array_push to get your result:

<?php

$string = "Php,Arrays,Mysql";

function backwards($input)
{
    $str = $input;
    $revStr = array();
    $str = explode(",", $str);
    for ($x = 0; $x < count($str); $x++) {
        array_push($revStr, strrev($str[$x]));
    }
    return implode(',', $revStr);
}

$result =backwards($string);

echo $result;

?>

You can check the demo here

How do I reverse a set of comma delimited strings and return them in the original order in PHP?

5 Answers5