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Source of: /manual/en/language.oop5.typehinting.php

<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.oop5.inc";
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    0 => 'language.oop5.typehinting.php',
    1 => 'Type Hinting',
  ),
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?>
<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) or arrays (since PHP 5.1). However, if <a href="language.types.null.php" class="type NULL">NULL</a> is used
   as the default parameter value, it will be allowed as an argument for any
   later call.
  </p>
 
  <div class="example">
   <p><b>Example #1 Type Hinting examples</b></p>
    <div class="example-contents programlisting">
<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 />}<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 para"><p>
    Failing to satisfy the type hint results in a catchable fatal error.
   </p></div>
    <div class="example-contents programlisting">
<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 /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

   <div class="example-contents para"><p>
    Type hinting also works with functions:
   </p></div>
    <div class="example-contents programlisting">
<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">$var&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'Hello&nbsp;World'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">/**<br />&nbsp;*&nbsp;A&nbsp;test&nbsp;function<br />&nbsp;*<br />&nbsp;*&nbsp;First&nbsp;parameter&nbsp;must&nbsp;be&nbsp;an&nbsp;object&nbsp;of&nbsp;type&nbsp;MyClass<br />&nbsp;*/<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">MyFunction&nbsp;</span><span style="color: #007700">(</span><span style="color: #0000BB">MyClass&nbsp;$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 para"><p>
    Type hinting allowing NULL value:
   </p></div>
    <div class="example-contents programlisting">
<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>

  </div>
  <p class="para">
   Type Hints can only be of the <a href="language.types.object.php" class="type object">object</a> and <a href="language.types.array.php" class="type array">array</a>
   (since PHP 5.1) type. Traditional type hinting with <a href="language.types.integer.php" class="type int">int</a> and
   <a href="language.types.string.php" class="type string">string</a> isn&#039;t supported.
  </p>
 </div><?php manual_footer(); ?>
 
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