How can undeclared variables in PHP forms lead to issues with data display on output pages?

Undeclared variables in PHP forms can lead to issues with data display on output pages because if a variable is not set or initialized, PHP will throw an error when trying to display its value. To solve this issue, you can use isset() or empty() functions to check if the variable is set before displaying it on the output page. 

$name = isset($_POST['name']) ? $_POST['name'] : '';
$email = isset($_POST['email']) ? $_POST['email'] : '';

echo "Name: " . $name . "<br>";
echo "Email: " . $email;

Keywords

undeclared variables PHP forms data display output pages issues

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