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<title>Returns the first value from a queue</title>
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<h1 class="refname">pht\Queue::front</h1>
<p class="verinfo">(PECL pht >= 0.0.1)</p><p class="refpurpose"><span class="refname">pht\Queue::front</span> — <span class="dc-title">Returns the first value from a queue</span></p>
</div>
<div class="refsect1 description" id="refsect1-pht-queue.front-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">public</span> <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>pht\Queue::front</strong></span>
( <span class="methodparam">void</span>
)</div>
<p class="para rdfs-comment">
This method will remove a value from the front of the queue (in constant
time). Attempting to return the front value from an empty queue will result
in an <a href="class.error.html" class="classname">Error</a> exception.
</p>
<div class="caution"><strong class="caution">Caution</strong>
<p class="para">
Due to the fact that all values in a <a href="class.pht-queue.html" class="classname">pht\Queue</a> are
serialised, extracting a value from the queue will require it to be
deserialised. This can incur a noticeable performance hit if the inspection
of the queue's front value is performed within a loop.
</p>
</div>
</div>
<div class="refsect1 parameters" id="refsect1-pht-queue.front-parameters">
<h3 class="title">Parameters</h3>
<p class="para">This function has no parameters.</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-pht-queue.front-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
The value on the front of the queue.
</p>
</div>
<div class="refsect1 examples" id="refsect1-pht-queue.front-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4567">
<p><strong>Example #1 Retrieving the front value of a queue</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">());</span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
int(1)
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4568">
<p><strong>Example #2 Retrieving the front value in a loop (bad example - don't do this)</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">array_fill</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">2000</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">));<br /><br />for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700">< </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">()); ++</span><span style="color: #0000BB">$i</span><span style="color: #007700">); </span><span style="color: #FF8000">// quadratic runtime</span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4569">
<p><strong>Example #3 Retrieving the front value in a loop (good example)</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">use </span><span style="color: #0000BB">pht</span><span style="color: #007700">\</span><span style="color: #0000BB">Queue</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$queue </span><span style="color: #007700">= new </span><span style="color: #0000BB">Queue</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">push</span><span style="color: #007700">(</span><span style="color: #0000BB">array_fill</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">2000</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">$front </span><span style="color: #007700">= </span><span style="color: #0000BB">$queue</span><span style="color: #007700">-></span><span style="color: #0000BB">front</span><span style="color: #007700">(); </span><span style="color: #FF8000">// create a separate variable<br /></span><span style="color: #007700">for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= </span><span style="color: #0000BB">0</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700">< </span><span style="color: #0000BB">count</span><span style="color: #007700">(</span><span style="color: #0000BB">$front</span><span style="color: #007700">); ++</span><span style="color: #0000BB">$i</span><span style="color: #007700">); </span><span style="color: #FF8000">// linear runtime</span>
</span>
</code></div>
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