PHP try catch: Handle Exceptions with Multiple catch Blocks

try wraps code that might throw an exception. catch handles it.

index.php

PHP

<?php
try {
    $result = intdiv(10, 0);
    echo "Result: $result";   // skipped
} catch (DivisionByZeroError $e) {
    echo "Cannot divide by zero";
}

echo "\nThe script continues.";

Output

OUTPUT

1
2

Cannot divide by zero
The script continues.

When an exception is thrown inside try, PHP skips the rest of the try block and jumps to the matching catch. After the catch, the script goes on.

Several catch blocks

PHP checks the catch blocks from top to bottom and uses the first one that matches. Put the most specific exception first.

index.php

PHP

<?php
function load(string $json): array
{
    return json_decode($json, true, 512, JSON_THROW_ON_ERROR);
}

try {
    load("{bad json");
} catch (JsonException $e) {
    echo "Invalid JSON\n";
} catch (Exception $e) {
    echo "Some other exception\n";
}

Output

OUTPUT

Invalid JSON

One handler for several types

Use | to catch more than one class in one block.

index.php

PHP

<?php
try {
    throw new InvalidArgumentException("bad value");
} catch (InvalidArgumentException | RangeException $e) {
    echo "Input problem: " . $e->getMessage();
}

Output

OUTPUT

Input problem: bad value

catch without a variable (PHP 8.0+)

If you do not need the exception object, leave out the variable.

index.php

PHP

<?php
try {
    throw new RuntimeException("x");
} catch (RuntimeException) {
    echo "Something failed";
}

Output

OUTPUT

Something failed

Catching everything

catch (Throwable $e) catches exceptions and errors. Use it only at the edge of your program (to log and show a safe message), not deep inside code.

index.php

PHP

<?php
try {
    echo strlen([]);
} catch (Throwable $e) {
    echo get_class($e);
}

Output

OUTPUT

TypeError

Do not swallow exceptions

An empty catch hides problems.

index.php

PHP

<?php
try {
    saveOrder($order);
} catch (Exception $e) {
    // silence: the order is lost and nobody knows
}

Always do something: log it, tell the user, retry, or rethrow.

Rethrow with context

If you cannot handle an exception fully, wrap it in a new one and keep the original as previous.

index.php

PHP

<?php
function readConfig(string $file): array
{
    try {
        return json_decode(file_get_contents($file), true, 512, JSON_THROW_ON_ERROR);
    } catch (JsonException $e) {
        throw new RuntimeException("Config file $file is broken", 0, $e);
    }
}

try {
    file_put_contents("bad.json", "{oops");
    readConfig("bad.json");
} catch (RuntimeException $e) {
    echo $e->getMessage() . "\n";
    echo get_class($e->getPrevious());
}

Output

OUTPUT

1
2

Config file bad.json is broken
JsonException

Where to catch

Catch an exception where you can do something useful about it. A small helper function usually should not catch it, but let it travel up to code that knows what the user should see.

Exercise: a safe division

Write safeDivide(int $a, int $b): string that returns the result as text, or "Cannot divide by zero" if the division fails. Use try and catch.

Show a possible solution

index.php

PHP

<?php
function safeDivide(int $a, int $b): string
{
    try {
        return (string) intdiv($a, $b);
    } catch (DivisionByZeroError) {
        return "Cannot divide by zero";
    }
}

echo safeDivide(9, 3) . "\n";
echo safeDivide(1, 0);

Output

OUTPUT

1
2

3
Cannot divide by zero