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<title>Exchanges all keys with their associated values in an array</title>
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<h1 class="refname">array_flip</h1>
<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">array_flip</span> — <span class="dc-title">Exchanges all keys with their associated values in an array</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.array-flip-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">array</span> <span class="methodname"><strong>array_flip</strong></span>
( <span class="methodparam"><span class="type">array</span> <code class="parameter">$array</code></span>
)</div>
<p class="para rdfs-comment">
<span class="function"><strong>array_flip()</strong></span> returns an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> in flip
order, i.e. keys from <code class="parameter">array</code> become values and values
from <code class="parameter">array</code> become keys.
</p>
<p class="para">
Note that the values of <code class="parameter">array</code> need to be valid
keys, i.e. they need to be either <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> or
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>. A warning will be emitted if a value has the wrong
type, and the key/value pair in question <em class="emphasis">will not be included
in the result</em>.
</p>
<p class="para">
If a value has several occurrences, the latest key will be
used as its value, and all others will be lost.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.array-flip-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">array</code></dt>
<dd>
<p class="para">
An array of key/value pairs to be flipped.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.array-flip-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the flipped array on success and <strong><code>NULL</code></strong> on failure.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.array-flip-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-6160">
<p><strong>Example #1 <span class="function"><strong>array_flip()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$input </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"oranges"</span><span style="color: #007700">, </span><span style="color: #DD0000">"apples"</span><span style="color: #007700">, </span><span style="color: #DD0000">"pears"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$flipped </span><span style="color: #007700">= </span><span style="color: #0000BB">array_flip</span><span style="color: #007700">(</span><span style="color: #0000BB">$input</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$flipped</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[oranges] => 0
[apples] => 1
[pears] => 2
)
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6161">
<p><strong>Example #2 <span class="function"><strong>array_flip()</strong></span> example : collision</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$input </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"a" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">"b" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">"c" </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$flipped </span><span style="color: #007700">= </span><span style="color: #0000BB">array_flip</span><span style="color: #007700">(</span><span style="color: #0000BB">$input</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$flipped</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
(
[1] => b
[2] => c
)
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.array-flip-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.array-values.html" class="function" rel="rdfs-seeAlso">array_values()</a> - Return all the values of an array</span></li>
<li class="member"><span class="function"><a href="function.array-keys.html" class="function" rel="rdfs-seeAlso">array_keys()</a> - Return all the keys or a subset of the keys of an array</span></li>
<li class="member"><span class="function"><a href="function.array-reverse.html" class="function" rel="rdfs-seeAlso">array_reverse()</a> - Return an array with elements in reverse order</span></li>
</ul>
</p>
</div>
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