ComponentsFuture::catch

Future::catch ​

(PHP 8.6+, True Async 1.0)

php
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
<?php

use Async\Future;
use Async\FutureState;

$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
<?php

use Async\Future;
use Async\FutureState;

$state  = new FutureState();
$source = new Future($state);

\Async\spawn(function() use ($state) {
    try {
        $response = httpGet('https://api.example.com/users');
        if ($response->status !== 200) {
            throw new \RuntimeException("HTTP error: {$response->status}");
        }
        $state->complete(json_decode($response->body, true));
    } catch (\Throwable $e) {
        $state->error($e);
    }
});

$future = $source
    ->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";

See also ​