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  <title>Type Hinting</title>

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</div><hr /><div id="language.oop5.typehinting" class="sect1">
  <h2 class="title">Type Hinting</h2>
  <p class="para">
   PHP 5 introduces type hinting. Functions are now able to force parameters
   to be objects (by specifying the name of the class in the function
   prototype), interfaces, arrays (since PHP 5.1) or <span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span>
   (since PHP 5.4). However, if <span class="type"><a href="language.types.null.html" class="type NULL">NULL</a></span> is used
   as the default parameter value, it will be allowed as an argument for any 
   later call.
  </p>
  
  <p class="para">
   If class or interface is specified as type hint then all its children or
   implementations are allowed too.
  </p>
  
  <p class="para">
   Type hints can not be used with scalar types such as <span class="type"><a href="language.types.integer.html" class="type int">int</a></span> or
   <span class="type"><a href="language.types.string.html" class="type string">string</a></span>.
   <a href="language.types.resource.html" class="link">Resources</a> and <a href="language.oop5.traits.html" class="link">Traits</a> are not allowed either.
  </p>
  
  <div class="example" id="example-227">
   <p><strong>Example #1 Type Hinting examples</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;An&nbsp;example&nbsp;class<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">/**<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;A&nbsp;test&nbsp;function<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;an&nbsp;object&nbsp;of&nbsp;type&nbsp;OtherClass<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*/<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">public&nbsp;function&nbsp;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">OtherClass&nbsp;$otherclass</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$otherclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">var</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br /><br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">/**<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;Another&nbsp;test&nbsp;function<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;an&nbsp;array<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*/<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">public&nbsp;function&nbsp;</span><span style="color: #0000BB">test_array</span><span style="color: #007700">(array&nbsp;</span><span style="color: #0000BB">$input_array</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$input_array</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">/**<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;iterator<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*/<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">public&nbsp;function&nbsp;</span><span style="color: #0000BB">test_interface</span><span style="color: #007700">(</span><span style="color: #0000BB">Traversable&nbsp;$iterator</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">get_class</span><span style="color: #007700">(</span><span style="color: #0000BB">$iterator</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">/**<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;callable<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*/<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">public&nbsp;function&nbsp;</span><span style="color: #0000BB">test_callable</span><span style="color: #007700">(</span><span style="color: #0000BB">callable&nbsp;$callback</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$data</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #0000BB">$callback</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$data</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;Another&nbsp;example&nbsp;class<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">OtherClass&nbsp;</span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;public&nbsp;</span><span style="color: #0000BB">$var&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'Hello&nbsp;World'</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

   <div class="example-contents"><p>
    Failing to satisfy the type hint results in a catchable fatal error.
   </p></div>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;An&nbsp;instance&nbsp;of&nbsp;each&nbsp;class<br /></span><span style="color: #0000BB">$myclass&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$otherclass&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">OtherClass</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;Fatal&nbsp;Error:&nbsp;Argument&nbsp;1&nbsp;must&nbsp;be&nbsp;an&nbsp;object&nbsp;of&nbsp;class&nbsp;OtherClass<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #DD0000">'hello'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Fatal&nbsp;Error:&nbsp;Argument&nbsp;1&nbsp;must&nbsp;be&nbsp;an&nbsp;instance&nbsp;of&nbsp;OtherClass<br /></span><span style="color: #0000BB">$foo&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">stdClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">$foo</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Fatal&nbsp;Error:&nbsp;Argument&nbsp;1&nbsp;must&nbsp;not&nbsp;be&nbsp;null<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">null</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Works:&nbsp;Prints&nbsp;Hello&nbsp;World<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">$otherclass</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Fatal&nbsp;Error:&nbsp;Argument&nbsp;1&nbsp;must&nbsp;be&nbsp;an&nbsp;array<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test_array</span><span style="color: #007700">(</span><span style="color: #DD0000">'a&nbsp;string'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Works:&nbsp;Prints&nbsp;the&nbsp;array<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test_array</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'a'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'c'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">//&nbsp;Works:&nbsp;Prints&nbsp;ArrayObject<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test_interface</span><span style="color: #007700">(new&nbsp;</span><span style="color: #0000BB">ArrayObject</span><span style="color: #007700">(array()));<br /><br /></span><span style="color: #FF8000">//&nbsp;Works:&nbsp;Prints&nbsp;int(1)<br /></span><span style="color: #0000BB">$myclass</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">test_callable</span><span style="color: #007700">(</span><span style="color: #DD0000">'var_dump'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

   <div class="example-contents"><p>
    Type hinting also works with functions:
   </p></div>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;An&nbsp;example&nbsp;class<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">MyClass&nbsp;</span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;public&nbsp;</span><span style="color: #0000BB">$var&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'Hello&nbsp;World'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">/**<br />&nbsp;*&nbsp;A&nbsp;test&nbsp;function<br />&nbsp;*<br />&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;an&nbsp;object&nbsp;of&nbsp;type&nbsp;MyClass<br />&nbsp;*/<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">myFunction</span><span style="color: #007700">(</span><span style="color: #0000BB">MyClass&nbsp;$foo</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$foo</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">var</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;Works<br /></span><span style="color: #0000BB">$myclass&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">MyClass</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">myFunction</span><span style="color: #007700">(</span><span style="color: #0000BB">$myclass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

   <div class="example-contents"><p>
    Type hinting allowing NULL value:
   </p></div>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br /></span><span style="color: #FF8000">/*&nbsp;Accepting&nbsp;NULL&nbsp;value&nbsp;*/<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">stdClass&nbsp;$obj&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">NULL</span><span style="color: #007700">)&nbsp;{<br /><br />}<br /><br /></span><span style="color: #0000BB">test</span><span style="color: #007700">(</span><span style="color: #0000BB">NULL</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">test</span><span style="color: #007700">(new&nbsp;</span><span style="color: #0000BB">stdClass</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

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