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<h1 class="refname">SplHeap::compare</h1>
<p class="verinfo">(PHP 5 >= 5.3.0)</p><p class="refpurpose"><span class="refname">SplHeap::compare</span> — <span class="dc-title">Compare elements in order to place them correctly in the heap while sifting up.</span></p>
</div>
<div class="refsect1 description" id="refsect1-splheap.compare-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">abstract</span> <span class="modifier">protected</span> <span class="type">int</span> <span class="methodname"><strong>SplHeap::compare</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value1</code></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value2</code></span>
)</div>
<p class="para rdfs-comment">
Compare <em><code class="parameter">value1</code></em> with <em><code class="parameter">value2</code></em>.
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
Throwing exceptions in <span class="methodname"><strong>SplHeap::compare()</strong></span> can
corrupt the Heap and place it in a blocked state. You can unblock it by
calling <span class="methodname"><a href="splheap.recoverfromcorruption.html" class="methodname">SplHeap::recoverFromCorruption()</a></span>.
However, some elements might not be placed correctly and it may hence
break the heap-property.
</p>
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<div class="refsect1 parameters" id="refsect1-splheap.compare-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">value1</code></em></span>
<dd>
<p class="para">
The value of the first node being compared.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">value2</code></em></span>
<dd>
<p class="para">
The value of the second node being compared.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-splheap.compare-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Result of the comparison, positive integer if <em><code class="parameter">value1</code></em> is greater than <em><code class="parameter">value2</code></em>, 0 if they are equal, negative integer otherwise.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Having multiple elements with the same value in a Heap is not recommended. They will end up in an arbitrary relative position.
</p>
</p></blockquote>
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