Future::catch

(PHP 8.6+, True Async 1.0)

public function catch(callable $catch): Future

Registers an error handler for the Future. The callback is invoked if the Future completed with an exception. If the callback returns a value, it becomes the result of the new Future. If the callback throws an exception, the new Future completes with that error.

Parameters

catch — the error handling function. Receives a Throwable, may return a value for recovery. Signature: function(\Throwable $e): mixed.

Return value

Future — a new Future with the error handling result, or with the original value if there was no error.

Examples

Example #1 Error handling with recovery

<?php

use Async\Future;

$future = Future::failed(new \RuntimeException("Service unavailable"))
    ->catch(function(\Throwable $e) {
        echo "Error: " . $e->getMessage() . "\n";
        return "default value"; // Recovery
    });

$result = $future->await();
echo $result; // default value

Example #2 Catching errors in async operations

<?php

use Async\Future;

$future = \Async\async(function() {
    $response = httpGet('https://api.example.com/users');
    if ($response->status !== 200) {
        throw new \RuntimeException("HTTP error: {$response->status}");
    }
    return json_decode($response->body, true);
})
->catch(function(\Throwable $e) {
    // Log the error and return an empty array
    error_log("API error: " . $e->getMessage());
    return [];
})
->map(function(array $users) {
    return count($users);
});

$count = $future->await();
echo "Users found: $count\n";

Documentation