Reverse string without strrev

Question

Some time ago during a job interview I got the task to reverse a string in PHP without using strrev.

My first solution was something like this:

Answer 1

You could also use a recursion to reverse the string. Something like this for example:

function reverse($s) {

    if(strlen($s) === 1) return $s;

    return substr($s, strlen($s)-1) . reverse(substr($s , 0, strlen($s)-1));
}

What you do here is actually returning the last character of the string and then calling again the same function with the substring that contains the initial string without the last character. When you reach the point when your string is just one character then you end the recursion.

Answer 2

That's an interesting one. Here's something I just came up with:

$s = 'abcdefghijklm';
for($i=strlen($s)-1, $j=0; $j<$i; $i--, $j++) {
    list($s[$j], $s[$i]) = array($s[$i], $s[$j]);
}
echo $s;

list() can be used to assign a list of variables in one operation. So what I am doing is simply swapping characters (starting with first and last, then second-first and second-last and so on, till it reaches the middle of the string)

Output is mlkjihgfedcba. Not using any other variables than $s and the counters, so I hope that fits your criteria.

Answer 3

This is my solution to solve this.

$in = 'This is a test text';
$out = '';
// find string length
$len = strlen($in);

// loop through it and print  it reverse
for ( $i = $len - 1; $i >=0;$i-- )
{
    $out = $out.$in[$i];
 }

echo $out;

Answer 4

Its Too Simple

//Reverse a String

$string = 'Basant Kumar';
$length = strlen($string);

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

Answer 5

public function checkString($str){
    if(!empty($str)){ 
        $i = 0;
        $str_reverse = '';

        while(isset($str[$i])){ 
            $strArr[] = $str[$i];
            $i++;
        }
        for($j = count($strArr); $j>= 0; $j--){ 
            if(isset($strArr[$j])){
                $str_reverse .= $strArr[$j];
            }
        }
        if($str == $str_reverse){ 
            echo 'It is a correct string';
        }else{
            echo 'Invalid string';
        }
    }
    else{
        echo 'string not found.';
    }
}

Answer 6

i have used some built in function but without str_rev function .

<?php


$text = "red";

$arr = str_split($text);

$rev_text =  array_reverse($arr);

echo join(" ",$rev_text);


?>