checkbox - How to use && opertor with checkboxes in php

Solution:

Demo: http://phpfiddle.org/main/code/0aix-4tdb

<form method="post" action="">
    <span>Select languages</span><br/>
    <input type="checkbox" name='lang[]' value="PHP"> PHP <br/>
    <input type="checkbox" name='lang[]' value="JavaScript"> JavaScript <br/>
    <input type="checkbox" name='lang[]' value="jQuery"> jQuery <br/>
    <input type="checkbox" name='lang[]' value="Angular JS"> Angular JS <br/>

    <input type="submit" value="Submit" name="submit">
</form>

<?php
if(isset($_POST['submit'])){

    if(!empty($_POST['lang'])) {

        foreach($_POST['lang'] as $value){
            echo $value.'<br/>';
        }

    }

}
?>

Solution:

you don't have to use && in the 3rd isset().

isset() will return true only if all arguments to isset() are set and do not contain null

So instead of doing,

if(isset($firstname && $lastname)){
    
            $sql = "SELECT firstname,lastname from biodata";
            $stmt = $pdo->query($sql);
}

do,

if(isset($firstname , $lastname)){
    
            $sql = "SELECT firstname,lastname from biodata";
            $stmt = $pdo->query($sql);
 }

For further details, you can visit PHP isset() with multiple parameters