Codeigniter中的文本更新和图像问题

Question

I am so tried When i update my text fields and also update image then update successfully but when in update only text fields or not update image then my old image is deleted from the database in Codeigniter.

controller

function blog_walk_update($id){

    $this->_checkAuthorized(self::CATEGORY_ID,'w');
    $_POST['id'] = $id; 
    //start
    if($_FILES['file_name']!=""){
        $storeFolder = './photo/uploads/';
        $pics = array();
        $file = $_FILES['file_name']['name'];
        $tempFile = $_FILES['file_name']['tmp_name'];
        $targetPath = $storeFolder .DIRECTORY_SEPARATOR;
        $targetFile =  $targetPath. $file;
        if(move_uploaded_file($tempFile,$targetFile)){
            array_push($pics,array("img"=>"/".$targetFile));
        }
        $_POST['file_name'] = $file;
    }else{
        $_POST['file_name'] = $file;
    }

    /////end

    $this->blog->blog_walk_update($_POST);
    redirect('/admin/blog/walk');
}

model

function blog_walk_update($data){
            $id = addslashes($data['id']);
            $t_name = addslashes($data['t_name']);
            $t_desp = addslashes($data['t_desp']);
            $file_name = addslashes($data['file_name']);
            $area_id = addslashes($data['area_id']);
            return $this->db->query("UPDATE walk_area  SET t_name = '$t_name', t_desp = '$t_desp', area_id = '$area_id',file_name = '$file_name'  WHERE id = '$id'");
        }

view

<div class="form-group">
    <label class="col-sm-2 control-label">Upload Image</label>
    <div class="col-sm-4">
        <img src="<?php echo base_url()."photo/uploads/".$walks->file_name  ?>" style ="width: 100px;">    
        <input type="file" value="<?= $walks->file_name; ?>" name="file_name" id="file" /><br/>
    </div>
</div>

Thanks in advance

Answer 1

You are showing image in image tag so keep file field value blank

<input type="file" value="" name="file_name" id="file" /><br/>

and check value in post data. When you change image you will get the field value in post data

function blog_walk_update($data){

$id = addslashes($data['id']);

$t_name = addslashes($data['t_name']);

$t_desp = addslashes($data['t_desp']);

$area_id = addslashes($data['area_id']);

if(isset($data['file_name']) && $data['file_name']!=''){

$file_name = addslashes($data['file_name']);
    return $this->db->query("UPDATE walk_area  SET t_name = '$t_name', t_desp = '$t_desp', area_id = '$area_id',file_name = '$file_name'  WHERE id = '$id'");

}else{

    return $this->db->query("UPDATE walk_area  SET t_name = '$t_name', t_desp = '$t_desp', area_id = '$area_id'  WHERE id = '$id'");

} 

}