Add Slider using Bootstrap Carousel with PHP code

I am trying to get all certificates from database to show on slider, My slide show only one image while it gets the count of images correct, this is the code I was trying to show images with.
using PHP and Bootstrap for carousel viewer.

<div class="row border rounded-lg" style="text-align: center; margin-right: 150px; margin-left: 180px;">
  <div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
     <ol class="carousel-indicators">
     <?php 
          $certificates = new Certificates();
          $a=0;
          if($certificates->getEmpCeretificate($_GET['id'])) {
             foreach($certificates->getEmpCeretificate($_GET['id']) as $certificate) {
                if($a==0){
                  echo '<li data-target="#carouselExampleIndicators" data-slide-to="'.$a.'" class="active"></li>';
                  }
                else{
                  echo '<li data-target="#carouselExampleIndicators" data-slide-to="'.$a.'"></li>';
                  }
                  $a = $a + 1 ;
                }
              }
              ?>
     </ol>
     <div class="carousel-inner">
         <?php 
         $b=0;
         if($certificates->getEmpCeretificate($_GET['id'])) {
            foreach($certificates->getEmpCeretificate($_GET['id']) as $certificate) {
              $image = base64_encode($certificate['certificate_image']); 
              echo '<p> '. $certificate['cnt'] . '</p>' ;
              if($b==0){
                  echo '<div class="carousel-item active" >'; 
              }
              else{
                 echo '<div class="carousel-item" >'; 
              }
                 echo '<img class="d-block w-100" src="data:image/jpg;charset=utf8;base64,'. $image .'"  style="width: 100%; height:300px;" />';
                 echo ' <div class="carousel-caption">';
                 echo ' <h3>'.  $certificate['name'] .'</h3>';
                 echo ' </div>';
                 echo '</div>';
                 $b = $b + 1 ;                 
                }
              }