convert.php

<?php                                                                           
if ($handle = opendir('.')) {                                                   
    while (false !== ($entry = readdir($handle))) {                             
        if ($entry != "." && $entry != "..") {                                  
            $fileInfo = explode('.', $entry);                                   
            $fileName = $fileInfo[0];                                           
            $fileExt = $fileInfo[1];                                            
            if ($fileExt === 'png') {                                           
                continue;                                                       
            }                                                                   
            echo $entry;                                                        
            exec('dwebp '.$entry.' -o '.$fileName.'.png', $a, $b);              
            if ($b != 0) {                                                      
                echo 'not webp';                                                
            } else {                                                            
                exec('convert '.$fileName.'.png '.$entry, $a, $b);              
                if ($b == 0) {                                                  
                    echo 'success';                                             
                }                                                               
            }                                                                   
            echo PHP_EOL;                                                       
        }                                                                       
    }                                                                           
    closedir($handle);                                                          
}