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    <h3>Editing: Callback.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/**
 * This file is part of the Nette Framework (https://nette.org)
 * Copyright (c) 2004 David Grudl (https://davidgrudl.com)
 */

declare(strict_types=1);

namespace Nette\Utils;

use Nette;
use function is_array, is_object, is_string;


/**
 * PHP callable tools.
 */
final class Callback
{
	use Nette\StaticClass;

	/**
	 * @param  string|object|callable  $callable  class, object, callable
	 * @deprecated use Closure::fromCallable()
	 */
	public static function closure($callable, ?string $method = null): \Closure
	{
		trigger_error(__METHOD__ . '() is deprecated, use Closure::fromCallable().', E_USER_DEPRECATED);
		try {
			return \Closure::fromCallable($method === null ? $callable : [$callable, $method]);
		} catch (\TypeError $e) {
			throw new Nette\InvalidArgumentException($e-&gt;getMessage());
		}
	}


	/**
	 * Invokes callback.
	 * @return mixed
	 * @deprecated
	 */
	public static function invoke($callable, ...$args)
	{
		trigger_error(__METHOD__ . '() is deprecated, use native invoking.', E_USER_DEPRECATED);
		self::check($callable);
		return $callable(...$args);
	}


	/**
	 * Invokes callback with an array of parameters.
	 * @return mixed
	 * @deprecated
	 */
	public static function invokeArgs($callable, array $args = [])
	{
		trigger_error(__METHOD__ . '() is deprecated, use native invoking.', E_USER_DEPRECATED);
		self::check($callable);
		return $callable(...$args);
	}


	/**
	 * Invokes internal PHP function with own error handler.
	 * @return mixed
	 */
	public static function invokeSafe(string $function, array $args, callable $onError)
	{
		$prev = set_error_handler(function ($severity, $message, $file) use ($onError, &amp;$prev, $function): ?bool {
			if ($file === __FILE__) {
				$msg = ini_get('html_errors')
					? Html::htmlToText($message)
					: $message;
				$msg = preg_replace(&quot;#^$function\\(.*?\\): #&quot;, '', $msg);
				if ($onError($msg, $severity) !== false) {
					return null;
				}
			}

			return $prev ? $prev(...func_get_args()) : false;
		});

		try {
			return $function(...$args);
		} finally {
			restore_error_handler();
		}
	}


	/**
	 * Checks that $callable is valid PHP callback. Otherwise throws exception. If the $syntax is set to true, only verifies
	 * that $callable has a valid structure to be used as a callback, but does not verify if the class or method actually exists.
	 * @param  mixed  $callable
	 * @return callable
	 * @throws Nette\InvalidArgumentException
	 */
	public static function check($callable, bool $syntax = false)
	{
		if (!is_callable($callable, $syntax)) {
			throw new Nette\InvalidArgumentException(
				$syntax
				? 'Given value is not a callable type.'
				: sprintf(&quot;Callback '%s' is not callable.&quot;, self::toString($callable))
			);
		}

		return $callable;
	}


	/**
	 * Converts PHP callback to textual form. Class or method may not exists.
	 * @param  mixed  $callable
	 */
	public static function toString($callable): string
	{
		if ($callable instanceof \Closure) {
			$inner = self::unwrap($callable);
			return '{closure' . ($inner instanceof \Closure ? '}' : ' ' . self::toString($inner) . '}');
		} elseif (is_string($callable) &amp;&amp; $callable[0] === &quot;\0&quot;) {
			return '{lambda}';
		} else {
			is_callable(is_object($callable) ? [$callable, '__invoke'] : $callable, true, $textual);
			return $textual;
		}
	}


	/**
	 * Returns reflection for method or function used in PHP callback.
	 * @param  callable  $callable  type check is escalated to ReflectionException
	 * @return \ReflectionMethod|\ReflectionFunction
	 * @throws \ReflectionException  if callback is not valid
	 */
	public static function toReflection($callable): \ReflectionFunctionAbstract
	{
		if ($callable instanceof \Closure) {
			$callable = self::unwrap($callable);
		}

		if (is_string($callable) &amp;&amp; strpos($callable, '::')) {
			return new \ReflectionMethod($callable);
		} elseif (is_array($callable)) {
			return new \ReflectionMethod($callable[0], $callable[1]);
		} elseif (is_object($callable) &amp;&amp; !$callable instanceof \Closure) {
			return new \ReflectionMethod($callable, '__invoke');
		} else {
			return new \ReflectionFunction($callable);
		}
	}


	/**
	 * Checks whether PHP callback is function or static method.
	 */
	public static function isStatic(callable $callable): bool
	{
		return is_string(is_array($callable) ? $callable[0] : $callable);
	}


	/**
	 * Unwraps closure created by Closure::fromCallable().
	 * @return callable|array
	 */
	public static function unwrap(\Closure $closure)
	{
		$r = new \ReflectionFunction($closure);
		$class = $r-&gt;getClosureScopeClass();
		if (substr($r-&gt;name, -1) === '}') {
			return $closure;

		} elseif (($obj = $r-&gt;getClosureThis()) &amp;&amp; $class &amp;&amp; get_class($obj) === $class-&gt;name) {
			return [$obj, $r-&gt;name];

		} elseif ($class) {
			return [$class-&gt;name, $r-&gt;name];

		} else {
			return $r-&gt;name;
		}
	}
}
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