Exceptions

Exception Message

An exception can carry a short message that explains the failure.

message The message is data; the catch block decides whether to expose it.

Exception Message

age
exception_message.php
Replay: real traced execution (multi-file project)
<?php
$age = 17;

try {
    if ($age < 18) {
        throw new Exception("too young");
    }

    $message = "allowed";
} catch (Exception $error) {
    $message = $error->getMessage();
}

echo "age=" . $age . "\n";
echo "message=" . $message . "\n";

<?php
$age = 12;

try {
    if ($age < 18) {
        throw new Exception("too young");
    }

    $message = "allowed";
} catch (Exception $error) {
    $message = $error->getMessage();
}

echo "age=" . $age . "\n";
echo "message=" . $message . "\n";

<?php
$age = 25;

try {
    if ($age < 18) {
        throw new Exception("too young");
    }

    $message = "allowed";
} catch (Exception $error) {
    $message = $error->getMessage();
}

echo "age=" . $age . "\n";
echo "message=" . $message . "\n";

  1. $age ← 17

    1<?php2$age→ 17 = 17; //@age=12, 25

  2. if ($age < 18)

    4try {5    if ($age17 < 18) {6        throw new Exception("too young");7    }

  3. echo "age=" . $age . " ";

    10} catch (Exception $error) {11    $message = $error->getMessage();12}1314echo "age=" . $age17 . "\n";15echo "message=" . $messagetoo young . "\n";
    outputage=17
message=too young

  1. $age ← 12

    1<?php2$age→ 12 = 12;

  2. if ($age < 18)

    4try {5    if ($age12 < 18) {6        throw new Exception("too young");7    }

  3. echo "age=" . $age . " ";

    10} catch (Exception $error) {11    $message = $error->getMessage();12}1314echo "age=" . $age12 . "\n";15echo "message=" . $messagetoo young . "\n";
    outputage=12
message=too young

  1. $age ← 25, $message ← allowed

    1<?php2$age→ 25 = 25;34try {5    if ($age < 18) {6        throw new Exception("too young");7    }89    $message→ allowed = "allowed";10} catch (Exception $error) {11    $message = $error->getMessage();12}1314echo "age=" . $age25 . "\n";15echo "message=" . $messageallowed . "\n";
    outputage=25
message=allowed