Get $_POST from multiple checkboxes

html

checkboxes

form-handling

input-validation

byNikita Barsukov·Aug 11, 2024

Use the array method for multiple checkboxes, name="options[]", grouping checkboxes and packaging their selected values in an array. Simple form example:

<form method="post" action="handler.php">
    <input type="checkbox" name="options[]" value="Option1">
    <input type="checkbox" name="options[]" value="Option2">
    <input type="submit" value="Submit">
</form>

On the server side, gather these values with the help of $_POST in your PHP script:

$checkedOptions = $_POST['options'] ?? []; // No panic if nothing was checked!
foreach ($checkedOptions as $option) {
    // Proceed with individual $option
}

Handling the checkboxes (aka making them work)

Code the checkboxes

It all starts with coding the checkboxes right. Bundle the checkboxes in an array with name="someArray[]":

<input type="checkbox" name="someArray[]" value="Item1">
<input type="checkbox" name="someArray[]" value="Item2">

Loop through selections and make them shine

Loop through $_POST['someArray'] in your PHP script to use the checked values. This loop smartly sidesteps unchecked boxes:

// $_POST['someArray'] is like an amazing party where only checked items are invited
if(isset($_POST['someArray'])){
    foreach($_POST['someArray'] as $guest){
        // Do something fun with each $guest here
    }
}

Error handling: Avoid null pointer tragedies

Use the null coalescing operator (??) to prevent errors if no checkbox was checked:

$guestsAtTheParty = $_POST['someArray'] ?? []; // Empty party? Can't let that happen!

Real-life usability: Tackling an inbox

Imagine a mail inbox where you can select multiple messages to delete:

foreach ($guestsAtTheParty as $unwantedGuest) {
    // Code to kick $unwantedGuest out of the party (or delete the message)
}

The $_POST array makes identifying unwanted emails a breeze, simplifying actions on the server side.

Handling complex scenarios: Because life is complex!

Dynamic checkbox creation: When life throws you options

When adding checkboxes dynamically with PHP, consistency is key. Ensure that the name attribute remains uniform:

// Just casually making new checkboxes on the fly. NBD
foreach ($options as $option) {
    echo '<input type="checkbox" name="options[]" value="' . htmlspecialchars($option) . '"> I\'m a ' . htmlspecialchars($option) . ' checkbox!';
}

Unchecked defaults: Because everyone needs a back-up plan

Use hidden inputs to submit a default value when a checkbox remains unchecked:

<input type="checkbox" name="options[]" value="Option3">
<input type="hidden" name="options[]" value="Default"> // Can't face the void of nothingness, can we?

Large checkbox groups: The more, the merrier?

Be aware of PHP's max_input_vars limit. Toe the line or raise this limit as needed:

ini_set('max_input_vars', 10000); // Because we have more friends than PHP's default limit!

Staying safe: It's a jungle out there!

Always sanitize and **validate user inputs to prevent security breaches like XSS or SQL Injection:

// It feels like cleaning up after a party. But it's crucial. 
foreach($_POST['options'] as $option) {
    $secureOption = filter_input(INPUT_POST, $option, FILTER_SANITIZE_STRING);
    // $secureOption is now safe to deal with. Phew!
}