How to Catch \'Allowed Memory Size Exhausted\' Errors Gracefully in PHP?

Catching 'Allowed Memory Size Exhausted' Errors Gracefully in PHP

Handling fatal errors, such as 'Allowed memory size exhausted' errors, can be crucial for ensuring the stability and user-friendliness of PHP applications. While increasing the memory limit with ini_set() can be a quick solution, it's not always the best option.

To catch fatal errors more effectively, consider using the register_shutdown_function(). By registering a callback function using this method, you can check for errors using error_get_last() at script termination. Here's an example:

<code class="php">ini_set('display_errors', false);
error_reporting(-1);

set_error_handler(function($code, $string, $file, $line) {
    throw new ErrorException($string, null, $code, $file, $line);
});

register_shutdown_function(function() {
    $error = error_get_last();
    if (null !== $error) {
        echo 'Caught at shutdown';
    }
});

try {
    while (true) {
        $data .= str_repeat('#', PHP_INT_MAX);
    }
} catch (\Exception $exception) {
    echo 'Caught in try/catch';
}</code>

When running this code, you'll notice the output "Caught at shutdown" because fatal errors like 'Allowed memory size exhausted' terminate the script, causing the shutdown function to catch the error.

You can access the error details in the $error array within the shutdown function and tailor your response accordingly. For instance, you could redirect the request to a different URL or try processing the request with different parameters.

While error handling with register_shutdown_function() can be effective for catching fatal errors, it's recommended to set error_reporting() high (-1) and use error handling with set_error_handler() and ErrorException for all other errors.

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