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<title>Call a function for every element in an iterator</title>
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<div class="refnamediv">
<h1 class="refname">iterator_apply</h1>
<p class="verinfo">(PHP 5 >= 5.1.0, PHP 7)</p><p class="refpurpose"><span class="refname">iterator_apply</span> — <span class="dc-title">Call a function for every element in an iterator</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.iterator-apply-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>iterator_apply</strong></span>
( <span class="methodparam"><span class="type"><a href="class.traversable.html" class="type Traversable">Traversable</a></span> <code class="parameter">$iterator</code></span>
, <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$function</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter">$args</code><span class="initializer"> = <strong><code>NULL</code></strong></span></span>
] )</div>
<p class="para rdfs-comment">
Calls a function for every element in an iterator.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.iterator-apply-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">iterator</code></dt>
<dd>
<p class="para">
The iterator object to iterate over.
</p>
</dd>
<dt>
<code class="parameter">function</code></dt>
<dd>
<p class="para">
The callback function to call on every element.
This function only receives the given <code class="parameter">args</code>, so it
is nullary by default. If <em>count($args) === 3</em>, for
instance, the callback function is ternary.
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
The function must return <strong><code>TRUE</code></strong> in order to
continue iterating over the <code class="parameter">iterator</code>.
</span>
</p></blockquote>
</p>
</dd>
<dt>
<code class="parameter">args</code></dt>
<dd>
<p class="para">
An <span class="type"><a href="language.types.array.html" class="type array">array</a></span> of arguments; each element of
<code class="parameter">args</code> is passed to the callback
<code class="parameter">function</code> as separate argument.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.iterator-apply-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the iteration count.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.iterator-apply-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4841">
<p><strong>Example #1 <span class="function"><strong>iterator_apply()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">print_caps</span><span style="color: #007700">(</span><span style="color: #0000BB">Iterator $iterator</span><span style="color: #007700">) {<br /> echo </span><span style="color: #0000BB">strtoupper</span><span style="color: #007700">(</span><span style="color: #0000BB">$iterator</span><span style="color: #007700">-></span><span style="color: #0000BB">current</span><span style="color: #007700">()) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /> return </span><span style="color: #0000BB">TRUE</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$it </span><span style="color: #007700">= new </span><span style="color: #0000BB">ArrayIterator</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"Apples"</span><span style="color: #007700">, </span><span style="color: #DD0000">"Bananas"</span><span style="color: #007700">, </span><span style="color: #DD0000">"Cherries"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">iterator_apply</span><span style="color: #007700">(</span><span style="color: #0000BB">$it</span><span style="color: #007700">, </span><span style="color: #DD0000">"print_caps"</span><span style="color: #007700">, array(</span><span style="color: #0000BB">$it</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
APPLES
BANANAS
CHERRIES
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.iterator-apply-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.array-walk.html" class="function" rel="rdfs-seeAlso">array_walk()</a> - Apply a user supplied function to every member of an array</span></li>
</ul>
</p>
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