isset( ): Used to check if a variable (eg. $telephone_no) is "full"
empty(): Used to check if a variable is "empty"
Example1:
<?php
if (isset ($telephone_no))
{
echo "Here's your telephone number: $telephone_no";
}else
{
echo "Error: You must enter a telephone number";
}
Example 2:
<?php
$telephone_no="";
if (empty ($telephone_no))
{
echo "Error: you need to enter a telephone number";
} else
{
echo "Here's you telephone number: $telephone_no";
}
?>
