The PHP Closure::bindTo API performs a focused operation on an object or value. The examples below show its effect on actual data.
Returns a new Closure bound to the supplied object and optional class scope.
What Is Closure::bindTo in PHP?
Returns a new Closure bound to the supplied object and optional class scope.
Syntax:
Closure::bindTo(?object $newThis, object|string|null $newScope = ...): ?ClosureThe method accepts the following parameters:
$newThis— Required. The object instance to bind as $this inside the closure; use null for a static closure.$newScope— Optional. The class scope applied to the bound closure, if access rules require one.
Return type declared by PHP: ?Closure. The value or side effect is demonstrated in the examples below.
Example 1: Basic Usage
This example uses a small input to make the main behavior visible.
<?php
$originalClosure = function (): string { return $this->message; };
$targetObject = new class { public string $message = "approved"; };
$boundClosure = $originalClosure->bindTo($targetObject, $targetObject::class);
echo $boundClosure();Output:
approvedReturns a new Closure bound to the supplied object and optional class scope.
Example 2: A Different Input
A different set of values shows the same operation in another situation.
<?php
$originalClosure = function (): string { return $this->message; };
$targetObject = new class { public string $message = "verified"; };
$boundClosure = $originalClosure->bindTo($targetObject, $targetObject::class);
echo $boundClosure();Output:
verifiedBinding cannot turn arbitrary inaccessible class members into public API; minimize coupling to private state.
Practical Example: Applying the Feature
This example shows an application-style use of the feature, with its surrounding setup visible.
<?php
$originalClosure = function (): string { return $this->message; };
$targetObject = new class { public string $message = "checked"; };
$boundClosure = $originalClosure->bindTo($targetObject, $targetObject::class);
echo $boundClosure();Output:
checkedThe code is shown for learning. Adjust the class names, inputs and error handling to suit your application.
Important Behavior and Edge Cases
- Binding cannot turn arbitrary inaccessible class members into public API; minimize coupling to private state.
- Returns a new Closure bound to the supplied object and optional class scope.
- Observe differences in empty inputs, invalid states and optional extension availability where relevant.
Comparison With Related Approaches
| Approach | Important Difference |
|---|---|
Closure::bindTo | Returns a new Closure bound to the supplied object and optional class scope. |
| Named functions | Named functions have stable names; Closures are first-class callable objects that can capture or bind state. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
Ignoring the documented state or precondition of Closure::bindTo | Binding cannot turn arbitrary inaccessible class members into public API; minimize coupling to private state. |
| Expecting a different type of result | Read the declared return type and distinguish returned values from changes to the source object. |
| Assuming a related API works identically | Named functions have stable names; Closures are first-class callable objects that can capture or bind state. |
Key Takeaways
- Returns a new Closure bound to the supplied object and optional class scope.
- Binding cannot turn arbitrary inaccessible class members into public API; minimize coupling to private state.
- Use the example that matches the values, runtime version and dependencies in your application.
Closure::bindTo is useful when its behavior matches the data structure and lifecycle of your PHP application. Choose it with a clear understanding of its preconditions and returned values.