--- /dev/null
+<?php
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Constraint that evaluates against a specified closure.
+ */
+class PHPUnit_Framework_Constraint_Callback extends PHPUnit_Framework_Constraint
+{
+ private $callback;
+
+ /**
+ * @param callable $callback
+ *
+ * @throws PHPUnit_Framework_Exception
+ */
+ public function __construct($callback)
+ {
+ if (!is_callable($callback)) {
+ throw PHPUnit_Util_InvalidArgumentHelper::factory(
+ 1,
+ 'callable'
+ );
+ }
+
+ parent::__construct();
+
+ $this->callback = $callback;
+ }
+
+ /**
+ * Evaluates the constraint for parameter $value. Returns true if the
+ * constraint is met, false otherwise.
+ *
+ * @param mixed $other Value or object to evaluate.
+ *
+ * @return bool
+ */
+ protected function matches($other)
+ {
+ return call_user_func($this->callback, $other);
+ }
+
+ /**
+ * Returns a string representation of the constraint.
+ *
+ * @return string
+ */
+ public function toString()
+ {
+ return 'is accepted by specified callback';
+ }
+}