PHP Loop Stuck on one character - php

Question

i have some problem.
i just want my loop to run, but when i try to do it, it fails, it has to increment each letter by a few, but it doesn't take any new letters at all, why is this happening and what is the reason? in c ++ such code would work.
function accum('ZpglnRxqenU') {
// your code
$result = '';
$letters_result = '';
$letter_original = '';
$num_if_str = strlen($s);
$j = 0;
for ( $i=0; $i <= $num_if_str; $i++ )
{
$letter_original = substr($s, $i, $i+1);
$j = 0;
while($j == $i)
{
$letters_result = $letters_result . $letter_original;
$j++;
}
if($i != strlen($s))
{
$letters_result = $letters_result . '-';
}
}
return $letters_result;
}
It returns
- Expected: 'Z-Pp-Ggg-Llll-Nnnnn-Rrrrrr-Xxxxxxx-Qqqqqqqq-Eeeeeeeee-Nnnnnnnnnn-Uuuuuuuuuuu'
Actual : 'Z-----------'
what problem with what PHP code?

Answer 1

There are a number of problems here:
you're using $s but never initialise it
Your call to substr() uses an incorrect value for the length of substring to return
you're inner loop only runs while $i = $j, but you initialise $j to 0 so it will only run when $i is zero, i.e. for the first letter of the string.
There is a simpler way to do this. In PHP you can address individual characters in a string as if they were array elements, so no need for substr()
Further, you can use str_repeat() to generate the repeating strings, and if you store the expanded strings in an array you can join them all with implode().
Lastly, combining ucwords() and strtolower() returns the required case.
Putting it all together we get
<?php
$str = "ZpglnRxqenU";
$output = [];
for ($i = 0;$i<strlen($str);$i++) {
$output[] = str_repeat($str[$i], $i+1);
}
$output = ucwords(strtolower(implode('-',$output)),"-");
echo $output; // Z-Pp-Ggg-Llll-Nnnnn-Rrrrrr-Xxxxxxx-Qqqqqqqq-Eeeeeeeee-Nnnnnnnnnn-Uuuuuuuuuuu
Demo:https://3v4l.org/OoukZ

Answer 2

I don't have much more to add to #TangentiallyPerpendicular's answer as far as critique, other than you've made the classic while($i<=strlen($s)) off-by-one blunder. String bar will have a length of 3, but arrays are zero-indexed [eg: [ 0 => 'b', 1 => 'a', '2' => 'r' ]] so when you hit $i == strlen() at 3, that's an error.
Aside from that your approach, when corrected and made concise, would look like:
function accum($input) {
$result = '';
for ( $i=0, $len=strlen($input); $i < $len; $i++ ) {
$letter = substr($input, $i, 1);
for( $j=0; $j<=$i; $j++ ) {
$result .= $letter;
}
if($i != $len-1) {
$result .= '-';
}
}
return $result;
}
var_dump(accum('ZpglnRxqenU'));
Output:
string(76) "Z-pp-ggg-llll-nnnnn-RRRRRR-xxxxxxx-qqqqqqqq-eeeeeeeee-nnnnnnnnnn-UUUUUUUUUUU"
Also keep in mind that functions have their own isolated variable scope, so you don't need to namespace variables like $letters_foo which can make your code a bit confusing to the eye.