make sure atleast one checkbox is selected php - php

Question

I have a little mailing form with a few checkboxes. At least one of the boxes need to be selected before mailing should start.
My HTML:
<input type='checkbox' id='part1' name='box1' value='box1' checked>
<label for="part1">Voor Leden agenda</label>
<br/>
<input type='checkbox' id='part2' name='box2' value='box2' checked>
<label for="part2">Voor Leiding agenda</label>
<br/>
<input type='checkbox' id='part3' name='box3' value='box3' checked>
<label for="part3">Verhuur agenda</label>
<br/>
<button type='submit' name='send'/>send</button>
My PHP:
if (isset($_POST['box1'])) {
$box1 = 'yes';
} else {
$box1 = 'No';
}
if (isset($_POST['box2'])) {
$box2 = 'yes';
} else {
$box2 = 'No';
}
if (isset($_POST['box3'])) {
$box3 = 'yes';
} else {
$box3 = 'No';
}
i would like to have a script that gives a message like below if no checkbox is selected:
if()
{
echo "<p class='redfont'>no checkboxes are selected</p>";
echo "<p><a href='javascript:history.back();'>Click to go back</a></p>";
}
edit: how can I give this message with php, only if all boxes are unchecked

Answer 1

if(!isset($_POST['box1']) && !isset($_POST['box2']) && !isset($_POST['box3']))
{
// none is set
}
You could even apply De Morgan's law and write this equivalent expression
if(isset($_POST['box1']) || isset($_POST['box2']) || isset($_POST['box3']))
{
// at least one of them is set
}
You could even send those 3 parameters to 1 isset call but then that would check if all of them are set, which is not your requirement.

Answer 2

Try this:
if(isset($_POST["box1"]) || isset($_POST["box2"]) || isset($_POST["box3"])) {
if(isset($_POST['box1'])) {
$box1 = 'yes';
} else {
$box1 = 'No';
}
if(isset($_POST['box2'])) {
$box2 = 'yes';
} else {
$box2 = 'No';
}
if(isset($_POST['box3'])) {
$box3 = 'yes';
} else {
$box3 = 'No';
}
} else {
echo "<p class='redfont'>no checkboxes are selected</p>";
echo "<p><a href='javascript:history.back();'>Click to go back</a></p>";
}

Answer 3

This one is more readable I think:
$boxes = ['box1', 'box2', 'box3'];
$checked = [];
foreach($boxes as $box){
if(isset($_POST[$box])){
$checked[] = $box;
}
}
if(count($checked) == 0){
// no boxes checked
echo "<p class='redfont'>no checkboxes are selected</p>";
echo "<p><a href='javascript:history.back();'>Click to go back</a></p>";
}else{
// at least one box is checked, you can do another foreach statement
with the $checked variable to do stuff with the checked ones
}

Answer 4

To do this for ANY number of checkboxes (Webistes are bound to expand), I assume all of you checkboxes are of the form box**i** :
if( strpos( implode(',' , array_keys($test)) , 'box' ) !== FALSE )

Answer 5

I use this function in JQuery:
jQuery.validation = function(){
var verif = 0;
$(':checkbox[id=list_exp]').each(function() {
if(this.checked == true){
verif++
}
});
if(verif == 0){
alert("no checkboxes are selected");
return false;
}
}