PHP需要复选框字段

I have a form with multiple checkboxes. I want to allow the user to select at least 1 in each checkbox field, if the user does not check any of the options in the checkbox, a message will display "You have to select at least one." How do I do it? I have here some of my codes:

<div>
    <div><span class="font-2">Categories:</span></div>
</div>

<div class = "addinfo">
    <?php $categories = array('Breakfast', 'Lunch', 'Dinner', 'Snack', 'Grill', 'Buffet', 'Fast Food');
          $values = explode(',' , $row['categories']);
    ?>

    <?php foreach($categories as $category) {
        $cat='';
        foreach($values as $value){
        if($value == $category){
        $cat ="checked";    
    }

    ?>
    <input <?php echo $cat ?> type="checkbox" name="category[]" value="<?php echo $category?>"><?php echo $category?><br>
    <?php } 
    }?>
</div>  

form

<form method = "POST" action = "<?php echo base_url().'/index.php/AdminController/operation'?>">

AdminController

public function addResto(){
    $this->load->model('AdminModel');
    $this->AdminModel->insert();
    $this->getRestos();
}
public function operation(){

    if(isset($_POST['btn'])){
        if(empty($_POST['id'])){
            $this->addResto();
        }
        else{
            $this->updatingResto();
        }   
    }
}
public function updateResto($id){
    $this->load->model('AdminModel');
    $restaurantinfo['restaurantinfo']=$this->AdminModel->getResto($id);
    $this->load->view('admin/UpdateRestoPage',$restaurantinfo);
}

public function updatePage(){
    $this->load->view('admin/UpdateRestoPage');
}

public function updatingResto(){
    $id = $_POST['id'];
    $this->load->model('AdminModel');
    $this->AdminModel->update($id);

}

You should also check if there is a checkbox that is checked

public function operation(){
    if(isset($_POST['btn'])){
        if(empty($_POST['category'])){
            $this->load->view('YOUR_VIEW_FILE',array('error'=>'category'));
        }else if(empty($_POST['id'])){
            $this->addResto();
        }
        else{
            $this->updatingResto();
        }   
    }
}

your view file add a condition

<?php 
    if(!empty($error) && $error=="category"){
?>
    <script>alert("You have to select at least one.");</script>
<?php 
    } 
?>

Add validation in your called php

<?php
    $checked = false;
    foreach($_POST["category"] as $key) {
        if(!empty($key)) {
            $checked = true;
        }
    }

    if(!$checked) {
        echo "<script>";
        echo "alert('You have to select at least one.');";
        echo "history.back();";
        echo "</script>";
        exit();
    }
?>

in your controllers operation function use

if (isset($_POST['mycheckbox'])) {
   echo "checked!";
} esle {
   //send again with error message
}

Using this validation in javascript: $("input:checkbox[name='a']:checked").length == 0

Example:

HTML code:
    <from name='frm1' method='' action='POST'>
        <label>Favorites:</label>
        <span>sports</span><input type="checkbox" name="fav" value="1"/>
        <span>music</span> <input type="checkbox" name="fav" value="2"/>
        <span>reading</span> <input type="checkbox" name="fav" value="3"/>
        <input type="button" value="validate">
    </form>

Javascript code:
    function validate() {
        //replace with your own code here
        if ($('input:checkbox[name="fav"]:checked').length == 0) {
            alert("You have to select at least one.");
        }
    }
    $("input[type='button']").click(validate)

It's just a simple example to demonstrate the use of :check selector(JQuery), you need to change and embed it in your project!

try to add this in your html code:

<script type="text/javascript">
function check () {
    var inputs = document.querySelectorAll("input[type='checkbox']");
    for(var i = 0; i < inputs.length; i++) {
        if (inputs[i].checked) {
            return true;
        }  
    }
    alert("You have to select at least one.");
    return false;
}
</script>

This one will show the error before the page refreshes. And add something like this in your html :

<input type = "button" onclick = "check();">

UPDATE : try to replace your code with this.

<div>
    <div><span class="font-2">Categories:</span></div>
</div>
<script type="text/javascript">
    function check () {
        var inputs = document.querySelectorAll("input[type='checkbox']");
        for(var i = 0; i < inputs.length; i++) {
            if (inputs[i].checked) {
                return true;
            }  
        }
        alert("You have to select at least one.");
        return false;
    }
</script>
<div class = "addinfo">
    <?php $categories = array('Breakfast', 'Lunch', 'Dinner', 'Snack', 'Grill', 'Buffet', 'Fast Food');
          $values = explode(',' , $row['categories']);
    ?>

    <?php foreach($categories as $category) {
        $cat='';
        foreach($values as $value){
        if($value == $category){
        $cat ="checked";    
    }

    ?>
    <input <?php echo $cat ?> type="checkbox" name="category[]" value="<?php echo $category?>"><?php echo $category?><br>
    <?php } 
    }?>
    <input type = "button" onclick = "check();">
</div>