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POPHP: __toString() and json_encode() not playing well together
 

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    <p>I've run into an odd problem and I'm not sure how to fix it. I have several classes that are all PHP implementations of JSON objects. Here' an illustration of the issue</p> <pre><code>class A { protected $a; public function __construct() { $this-&gt;a = array( new B, new B ); } public function __toString() { return json_encode( $this-&gt;a ); } } class B { protected $b = array( 'foo' =&gt; 'bar' ); public function __toString() { return json_encode( $this-&gt;b ); } } $a = new A(); echo $a; </code></pre> <p>The output from this is</p> <pre><code>[{},{}] </code></pre> <p>When the <em>desired</em> output is</p> <pre><code>[{"foo":"bar"},{"foo":"bar"}] </code></pre> <p>The problem is that I was relying on the __toString() hook to do my work for me. But it can't, because the serialize that json_encode() uses won't call __toString(). When it encounters a nested object it simply serializes public properties only.</p> <p>So, the question then become this: Is there a way I can develop a managed interface to JSON classes that both lets me use setters and getters for properties, but also allows me to get the JSON serialization behavior I desire?</p> <p>If that's not clear, here's an example of an implementation that <em>won't</em> work, since the __set() hook is only called for the initial assignment</p> <pre><code>class a { public function __set( $prop, $value ) { echo __METHOD__, PHP_EOL; $this-&gt;$prop = $value; } public function __toString() { return json_encode( $this ); } } $a = new a; $a-&gt;foo = 'bar'; $a-&gt;foo = 'baz'; echo $a; </code></pre> <p>I suppose I could also do something like this</p> <pre><code>class a { public $foo; public function setFoo( $value ) { $this-&gt;foo = $value; } public function __toString() { return json_encode( $this ); } } $a = new a; $a-&gt;setFoo( 'bar' ); echo $a; </code></pre> <p>But then I would have to rely on the diligence of the other developers to use the setters - I can't force adherence programmtically with this solution.</p> <p><strong>---> EDIT &lt;---</strong></p> <p>Now with a test of Rob Elsner's response</p> <pre><code>&lt;?php class a implements IteratorAggregate { public $foo = 'bar'; protected $bar = 'baz'; public function getIterator() { echo __METHOD__; } } echo json_encode( new a ); </code></pre> <p>When you execute this, you can see that the getIterator() method isn't ever invoked.</p>
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