How to validate multiple value (Array of value ) in single Input (form) in codeigniter - codeigniter

Question

this is the html part when i add more email id's only first email is being validated and rest of emails treat as normal even if they are not in proper
<form action="<?php echo base_url()?>index.php/EMail/show_email">
<div class="form-group">
<label for="exampleInputEmail1">To :</label>
<input type="email" name="toa[]" ng-model="to" placeholder="To" class=" tagsinput" value="ss" />
</div>
<div class="form-group">
<label for="exampleInputEmail1">Subject :</label>
<input type="text" class="form-control" ng-model="sub" name="suba" id="exampleInputEmail1" placeholder="Subject">
<div>{{sub}}</div>
</div>
<div class="form-group">
<label for="exampleInputEmail1">CC :</label>
<input type="text" class="form-control" ng-model="to" name="cca" id="exampleInputEmail1" placeholder="CC">
<div>{{to}}</div>
</div>
<div class="form-group">
<label for="exampleInputEmail1">BCC:</label>
<input type="text" class="form-control" name="bcca" id="exampleInputEmail1" placeholder="BCC">
</div>
<div class="form-group ">
<label for="ccomment" class="control-label">Message</label>
<textarea class="form-control " id="ccomment" name="msg" required></textarea>
</div>
<div class="form-group">
<label for="exampleInputFile">File input</label>
<input type="file" id="exampleInputFile">
<p class="help-block">Example block-level help text here.</p>
</div>
<div class="checkbox">
<label>
<input type="checkbox"> Check me out
</label>
</div>
<input type="submit" onclick="mail()" class="btn btn-primary" value="Send"/>
<button type="submit" class="btn btn-Success">Draft</button>
</form>
this is my controller and "toa "is that field which i mentioned in the image
function show_email(){
$this->form_validation->set_rules("toa[]","To","valid_email");
$this->form_validation->set_rules("cca","CC ","valid_email");
$this->form_validation->set_rules("suba","Subject","required");
$this->form_validation->set_rules("bcca","bcc","valid_email");
$this->form_validation->set_rules("msg","Message","required");
if($this->form_validation->run()==FALSE){
$data["title"]="EMail";
$this->load->view('header',$data);
$this->load->view('sidebar');
$this->load->view('Mail/mail');
}else{
//finish
$ccdata=$this->input->post("cca");
$bccdata=$this->input->post("bcca");
$sub=$this->input->post("suba");
$ms=$this->input->post("msg");
$dataa["username"]="MyProject";
$dataa["msg"]=$ms;
$msg=$this->load->view('Email_Temp/mail',$dataa,TRUE);
$todata=explode(",",$data);
print_r($todata[0]);
//$this->SendEmail($todata,$ccdata,$bccdata,$msg,$sub);
}
}
[Image] this is the field (to) that i want to validate