Problem in reading bytes array in codeigniter

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PHP

CodeIgniter

Hi, I am posting an agents name, father name and a JPEG image as array of bytes from android app to my codeigniter application and saving the received data in mysql data base table. The field type for storing image is Medium BLOB. But image bytes stored in database table are of IKB size. I do not know why the image bytes are lost. Here is my PHP code given below

$id = $this->input->post("AgentId");
$name = $this->input->post("name");
$father = $this->input->post("father");
$picture = $this->input->post("picture");
$data = array("AgentName" => $name, 
	"Father" => $father, 
	$picture" => $picture);

	$this->db->where("AgentId", $id);
	$this->db->update('agent', $data);

What I have tried:

I do not understand the issue I am new to code igniter