How to retrieve blob image from mysql database in ionic framework?

I've tried to retrieve image from my Mysql Database in my ionic project, but only succeed when I call it from a column which contains a url to the image. If I call from a blob column which have an uploaded picture, it shows nothing.

Here my PHP code to create JSON from mysql data

<?php
    header("Access-Control-Allow-Origin: *");
    header("Access-Control-Allow-Methods: GET, POST, PUT, DELETE");
    header("Access-Control-Allow-Headers: Authorization");

    $db_name  = 'mydb';
    $hostname = 'myhost';
    $username = 'myuser';
    $password = 'mypswd';
    $email = $_GET['email']; 

    $dbh = new PDO("mysql:host=$hostname;dbname=$db_name", $username, $password);


    $sql = 'SELECT * FROM users where  email != "' .$email. '"';

    $stmt = $dbh->prepare($sql);

    $stmt->execute();

    $result = $stmt->fetchAll( PDO::FETCH_ASSOC );

    $json = json_encode( $result );
    echo $json;
    ?>

Here my code to call a column contained a URL to the picture

 <ion-item class="item-avatar item-icon-right" ng-repeat="user in users" type="item-text-wrap" href="#/tab/users/{{auth.profile.name}}/{{user.id}}">
    <img ng-src={{user.avatar}}>
    .....
<ion-item>

Column avatar is contained a URL to an image

But when I try to call a blob column like :

<img ng-src={{user.photo}}> //photo contains a blob image

It just shows nothing.