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<title>Computes the difference of arrays using keys for comparison</title>
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<h1 class="refname">array_diff_key</h1>
<p class="verinfo">(PHP 5 >= 5.1.0)</p><p class="refpurpose"><span class="refname">array_diff_key</span> — <span class="dc-title">Computes the difference of arrays using keys for comparison</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.array-diff-key-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">array</span> <span class="methodname"><strong>array_diff_key</strong></span>
( <span class="methodparam"><span class="type">array</span> <code class="parameter">$array1</code></span>
, <span class="methodparam"><span class="type">array</span> <code class="parameter">$array2</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter">$...</code></span>
] )</div>
<p class="para rdfs-comment">
Compares the keys from <em><code class="parameter">array1</code></em> against the keys
from <em><code class="parameter">array2</code></em> and returns the difference.
This function is like <span class="function"><a href="function.array-diff.html" class="function">array_diff()</a></span> except the
comparison is done on the keys instead of the values.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.array-diff-key-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">array1</code></em></span>
<dd>
<p class="para">
The array to compare from
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">array2</code></em></span>
<dd>
<p class="para">
An array to compare against
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">...</code></em></span>
<dd>
<p class="para">
More arrays to compare against
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.array-diff-key-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> containing all the entries from
<em><code class="parameter">array1</code></em> whose keys are not present in any of the
other arrays.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.array-diff-key-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4939">
<p><strong>Example #1 <span class="function"><strong>array_diff_key()</strong></span> example</strong></p>
<div class="example-contents"><p>
The two keys from the <em>key => value</em> pairs are
considered equal only if
<em>(string) $key1 === (string) $key2 </em>. In other words
a strict type check is executed so the string representation must be
the same.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$array1 </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'blue' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'red' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #DD0000">'green' </span><span style="color: #007700">=> </span><span style="color: #0000BB">3</span><span style="color: #007700">, </span><span style="color: #DD0000">'purple' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$array2 </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'green' </span><span style="color: #007700">=> </span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #DD0000">'blue' </span><span style="color: #007700">=> </span><span style="color: #0000BB">6</span><span style="color: #007700">, </span><span style="color: #DD0000">'yellow' </span><span style="color: #007700">=> </span><span style="color: #0000BB">7</span><span style="color: #007700">, </span><span style="color: #DD0000">'cyan' </span><span style="color: #007700">=> </span><span style="color: #0000BB">8</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">array_diff_key</span><span style="color: #007700">(</span><span style="color: #0000BB">$array1</span><span style="color: #007700">, </span><span style="color: #0000BB">$array2</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(2) {
["red"]=>
int(2)
["purple"]=>
int(4)
}
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.array-diff-key-notes">
<h3 class="title">Notes</h3>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
This function only checks one dimension of a n-dimensional
array. Of course you can check deeper dimensions by using
<em>array_diff_key($array1[0], $array2[0]);</em>.
</p>
</p></blockquote>
</div>
<div class="refsect1 seealso" id="refsect1-function.array-diff-key-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.array-diff.html" class="function" rel="rdfs-seeAlso">array_diff()</a> - Computes the difference of arrays</span></li>
<li class="member"> <span class="function"><a href="function.array-udiff.html" class="function" rel="rdfs-seeAlso">array_udiff()</a> - Computes the difference of arrays by using a callback function for data comparison</span></li>
<li class="member"> <span class="function"><a href="function.array-diff-assoc.html" class="function" rel="rdfs-seeAlso">array_diff_assoc()</a> - Computes the difference of arrays with additional index check</span></li>
<li class="member"> <span class="function"><a href="function.array-diff-uassoc.html" class="function" rel="rdfs-seeAlso">array_diff_uassoc()</a> - Computes the difference of arrays with additional index check which is performed by a user supplied callback function</span></li>
<li class="member"> <span class="function"><a href="function.array-udiff-assoc.html" class="function" rel="rdfs-seeAlso">array_udiff_assoc()</a> - Computes the difference of arrays with additional index check, compares data by a callback function</span></li>
<li class="member"> <span class="function"><a href="function.array-udiff-uassoc.html" class="function" rel="rdfs-seeAlso">array_udiff_uassoc()</a> - Computes the difference of arrays with additional index check, compares data and indexes by a callback function</span></li>
<li class="member"> <span class="function"><a href="function.array-diff-ukey.html" class="function" rel="rdfs-seeAlso">array_diff_ukey()</a> - Computes the difference of arrays using a callback function on the keys for comparison</span></li>
<li class="member"> <span class="function"><a href="function.array-intersect.html" class="function" rel="rdfs-seeAlso">array_intersect()</a> - Computes the intersection of arrays</span></li>
<li class="member"> <span class="function"><a href="function.array-intersect-assoc.html" class="function" rel="rdfs-seeAlso">array_intersect_assoc()</a> - Computes the intersection of arrays with additional index check</span></li>
<li class="member"> <span class="function"><a href="function.array-intersect-uassoc.html" class="function" rel="rdfs-seeAlso">array_intersect_uassoc()</a> - Computes the intersection of arrays with additional index check, compares indexes by a callback function</span></li>
<li class="member"> <span class="function"><a href="function.array-intersect-key.html" class="function" rel="rdfs-seeAlso">array_intersect_key()</a> - Computes the intersection of arrays using keys for comparison</span></li>
<li class="member"> <span class="function"><a href="function.array-intersect-ukey.html" class="function" rel="rdfs-seeAlso">array_intersect_ukey()</a> - Computes the intersection of arrays using a callback function on the keys for comparison</span></li>
</ul>
</p>
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