number of consecutive occurrence of character followed by character

Ex input : 'zzzyyyyxxxwwvzz'

expected output : '3z4y3x2w1v2z'

code that I have tried

<?php
$str = "zzzyyyyxxxwwvzz";
$strArray = count_chars($str, 1);

foreach ($strArray as $key => $value)
{
    echo $value.chr($key);
}
?>

output is : 5z4y3x2w1v

• Using str_split function, get all characters in the given string in an array
• Now, using basic looping and conditionals, and storing previous character, you can determine if consecutive or not, and accordingly get the output string generated.

Try the following (explanation in code comments):

$input = 'zzzyyyyxxxwwvzz';

// Split full string into array of single characters
$input_chars = str_split($input);

// initialize some temp variables
$prev_char = '';
$consecutive_count = 0;

$output = '';

// Loop over the characters
foreach ($input_chars as $char) {

    // first time initialize the previous character
    if ( empty($prev_char) ) {
        $prev_char = $char;
        $consecutive_count++;
    } elseif ($prev_char === $char) { // current character matches previous character
        $consecutive_count++;
    } else { // not consecutive character
        // add to output string
        $output .= ($consecutive_count . $prev_char);

        // set current char as new previous_char
        $prev_char = $char;
        $consecutive_count = 1;
    }
}

// handle remaining characters
$output .= ($consecutive_count . $prev_char);
echo $output;

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