Reverse a string with php

问题

I am trying to find a way to reverse a string, I've seen alternatives but i wanted to to it this way thinking outside the box and not using anyone else's code as an alternative, the code below reverses the string but I keep getting this error:

Notice: Undefined offset: 25 in C:\wamp\www\test\index.php on line 15

25 being the length of the string which is being deincremented.

//error_reporting(NULL);
$string = trim("This is a reversed string");

//find length of string including whitespace
$len =strlen($string);

//slipt sting into an array
$stringExp = str_split($string);

//deincriment string and echo out in reverse
for ($i = $len; $i >=0;$i--)
{
echo $stringExp[$i];
}

thanks in advance

回答1:

As others said, there's strrev() to do this.

If you want to build it on your own (for learning?): your problem is that you're starting with your index one too high - a string of length 25 is indexed from 0 to 24, so your loop has to look like this:

for ($i = $len - 1; $i >=0;$i--)
{
   echo $stringExp[$i];
}

回答2:

You're trying much too hard, always consult the manual and/or a search engine to check if there are native functions to do what you want before you end up "reinventing the wheel":

strrev — Reverse a string

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

$string = "This is a reversed string";
echo strrev($string);
// Output: gnirts desrever a si sihT

回答3:

$string = 'mystring';
$length = strlen($string);

for ($i = $length; $i > 0; $i--){
echo $string[$i-1];
}

OUTPUT: gnirtsym

回答4:

You must get $len-1 because string starts from 0 to $len-1

回答5:

There is a function for this strrev

回答6:

echo strrev("This is a reversed string!"); 

回答7:

php is quite complete in term of string function you just need to pass the string . thats why php is easy :)

use strrev php function http://bg2.php.net/manual/en/function.strrev.php

<?php
  echo strrev("This is a reversed string");
 ?>

// Output: gnirts desrever a si sihT

回答8:

<?php
// Reversed string and Number
//  For Example :
    $str = "hello world. This is john duvey";
    $number = 123456789;
    $newStr = strrev($str);
    $newBum = strrev($number);

    echo $newStr;
    echo "<br />";
    echo $newBum;

OUTPUT : first : yevud nhoj si sihT .dlrow olleh second: 987654321

回答9:

for ($i = $len-1; $i >=0;$i--)
{
  echo $stringExp[$i];
}

Since the index starts at 0

回答10:

Change your for loop to

for ($i = $len-1; $i >=0;$i--)
{
echo $stringExp[$i];
}

回答11:

<?php
echo strrev("PHP TUTORS");
?>

OUTPUT OF THE ABOVE SCRIPT

SROTUT PHP

Reference Source Code

回答12:

You can use it:

echo $reversed_s = join(' ',array_reverse(explode(' ',"Hello World")));

回答13:

public function stringReverse($string="Jai mata di")
{
    $length = strlen($string) - 1;
    $i = 0;
    while ($i < $length + 1) {
        echo $string[$length - $i];
        $i++;

    }
}

回答14:

We can do String Reverse with help of following menthods

    $string = "Hello world!";

1. 1st way to do:

   echo strrev($string);
   

2. 2nd way to do:

    $stringSplit = str_split($string);
               for ($i = $len-1; $i >=0;$i--)
               {
               echo $stringSplit[$i];
               }
   

回答15:

This will work

class StringUtils {

    public function stringReverse($string){
        $arr1 = str_split($string);
        $arr2 = array();
        for($i = count($arr1); $i >= 0; $i--){
            $arr2[count($arr1) - $i] = $arr1[$i];
        }
        return implode("", $arr2);
    }
}

回答16:

<?php
/* Reverse a string with php */
echo strrev("Hello World!"); 
?>

Reverse a string php

回答17:

Find the length of string and through loop iterate it from length-1 to 0 then concatenate in temp variable.enter image description here

来源：https://stackoverflow.com/questions/11100634/reverse-a-string-with-php