interfaces.php

<?php

interface Lock {
    public function advisory(string $identifier): LockContext;
    public function exclusive(string $identifier): LockContext;
    public function waitForAdvisory(string $identifier, int $timeout = 0): \Generator;
    public function waitForExclusive(string $identifier, int $timeout = 0): \Generator;
}

interface LockContext {
    public function exec(callable $cb);
    public function release();
}

class LockContentionException extends \RuntimeException {}

sample_impl.php

<?php

class InMemoryLock implements Lock {
    private $advisory = [];
    private $exclusive = [];

    public function advisory(string $identifier): LockContext {
        if (isset($this->exclusive[$identifier])) {
            throw new LockContentionException("$identifier not available");
        }
        $this->advisory[$identifier] = $this->advisory[$identifier] ?? 0;
        $this->advisory[$identifier]++;
        return new CallbackLockContext(function() use ($identifier) {
            $this->release($identifier);
        });
    }

    public function exclusive(string $identifier): LockContext {
        if (isset($this->exclusive[$identifier]) || isset($this->advisory[$identifier])) {
            throw new LockContentionException("$identifier not available");
        }
        $this->exclusive[$identifier] = true;
        return new CallbackLockContext(function() use ($identifier) {
            $this->release($identifier);
        });
    }

    public function waitForAdvisory(string $identifier, int $timeout = 0): \Generator {
        $start = microtime(true);
        while (isset($this->exclusive[$identifier])) {
            if ($timeout !== 0 && microtime(true) - $start > $timeout * 1000) {
                throw new LockContentionException("Timeout locking $identifier: not available");
            }
            yield;
        }
        return $this->advisory($identifier);
    }

    public function waitForExclusive(string $identifier, int $timeout = 0): \Generator {
        $start = microtime(true);
        while (isset($this->exclusive[$identifier]) || isset($this->advisory[$identifier])) {
            if ($timeout !== 0 && microtime(true) - $start > $timeout * 1000) {
                throw new LockContentionException("Timeout locking $identifier: not available");
            }
            yield;
        }
        return $this->exclusive($identifier);
    }

    private function release(string $identifier) {
        if (isset($this->exclusive[$identifier])) {
            unset($this->exclusive[$identifier]);
        }
        if (isset($this->advisory[$identifier])) {
            $this->advisory[$identifier]--;
            if ($this->advisory[$identifier] <= 0) {
                unset($this->advisory[$identifier]);
            }
        }

    }
}

class CallbackLockContext implements LockContext {

    private $cb;
    private $released = false;

    public function __construct(callable $cb) {
        $this->cb = $cb;
    }

    public function __destruct() {
        $this->release();
    }

    public function exec(callable $cb) {
        try {
            return $cb();
        } finally {
            $this->release();
        }
    }

    public function release() {
        if ($this->released) {
            return;
        }
        $this->released = true;
        ($this->cb)();
    }
}