Cách kiểm tra xem một biến có trống hay không trong PHP

<?php
$var1 = '';
$var2 = 0;
$var3 = NULL;
$var4 = FALSE;
$var5 = array();
 
// Testing the variables
if(empty($var1)){
    echo 'This line is printed, because the $var1 is empty.';
}
echo "<br>";
 
if(empty($var2)){
    echo 'This line is printed, because the $var2 is empty.';
}
echo "<br>";
 
if(empty($var3)){
    echo 'This line is printed, because the $var3 is empty.';
}
echo "<br>";
 
if(empty($var4)){
    echo 'This line is printed, because the $var4 is empty.';
}
echo "<br>";
 
if(empty($var5)){
    echo 'This line is printed, because the $var5 is empty.';
}
?>