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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head>  <title>Calculate Levenshtein distance between two strings</title>  <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.lcfirst.html">lcfirst</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.localeconv.html">localeconv</a></div> <div class="up"><a href="ref.strings.html">String Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.levenshtein" class="refentry"> <div class="refnamediv">  <h1 class="refname">levenshtein</h1>  <p class="verinfo">(PHP 4 &gt;= 4.0.1, PHP 5)</p><p class="refpurpose"><span class="refname">levenshtein</span> &mdash; <span class="dc-title">Calculate Levenshtein distance between two strings</span></p> </div>  <div class="refsect1 description">  <h3 class="title">Description</h3>  <div class="methodsynopsis dc-description">   <span class="type">int</span> <span class="methodname"><b><b>levenshtein</b></b></span>    ( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$str1</tt></span>   , <span class="methodparam"><span class="type">string</span> <tt class="parameter">$str2</tt></span>   )</div>  <div class="methodsynopsis dc-description">   <span class="type">int</span> <span class="methodname"><b><b>levenshtein</b></b></span>    ( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$str1</tt></span>   , <span class="methodparam"><span class="type">string</span> <tt class="parameter">$str2</tt></span>   , <span class="methodparam"><span class="type">int</span> <tt class="parameter">$cost_ins</tt></span>   , <span class="methodparam"><span class="type">int</span> <tt class="parameter">$cost_rep</tt></span>   , <span class="methodparam"><span class="type">int</span> <tt class="parameter">$cost_del</tt></span>   )</div>  <p class="para rdfs-comment">   The Levenshtein distance is defined as the minimal number of   characters you have to replace, insert or delete to transform   <i><tt class="parameter">str1</tt></i> into <i><tt class="parameter">str2</tt></i>.   The complexity of the algorithm is <i>O(m*n)</i>,   where <i>n</i> and <i>m</i> are the   length of <i><tt class="parameter">str1</tt></i> and   <i><tt class="parameter">str2</tt></i> (rather good when compared to   <a href="function.similar-text.html" class="function">similar_text()</a>, which is O(max(n,m)**3),   but still expensive).  </p>  <p class="para">   In its simplest form the function will take only the two   strings as parameter and will calculate just the number of   insert, replace and delete operations needed to transform   <i><tt class="parameter">str1</tt></i> into <i><tt class="parameter">str2</tt></i>.  </p>  <p class="para">   A second variant will take three additional parameters that   define the cost of insert, replace and delete operations.  This   is more general and adaptive than variant one, but not as   efficient.  </p> </div><div class="refsect1 parameters">  <h3 class="title">Parameters</h3>  <p class="para">   <dl>    <dt>     <span class="term"><i><tt class="parameter">str1</tt></i></span>     <dd>      <p class="para">       One of the strings being evaluated for Levenshtein distance.      </p>     </dd>    </dt>    <dt>     <span class="term"><i><tt class="parameter">str2</tt></i></span>     <dd>      <p class="para">       One of the strings being evaluated for Levenshtein distance.      </p>     </dd>    </dt>    <dt>     <span class="term"><i><tt class="parameter">cost_ins</tt></i></span>     <dd>      <p class="para">       Defines the cost of insertion.      </p>     </dd>    </dt>    <dt>     <span class="term"><i><tt class="parameter">cost_rep</tt></i></span>     <dd>      <p class="para">       Defines the cost of replacement.      </p>     </dd>    </dt>    <dt>     <span class="term"><i><tt class="parameter">cost_del</tt></i></span>     <dd>      <p class="para">       Defines the cost of deletion.      </p>     </dd>    </dt>   </dl>  </p> </div>  <div class="refsect1 returnvalues">  <h3 class="title">Return Values</h3>  <p class="para">   This function returns the Levenshtein-Distance between the   two argument strings or -1, if one of the argument strings   is longer than the limit of 255 characters.  </p> </div>  <div class="refsect1 examples">  <h3 class="title">Examples</h3>  <p class="para">   <div class="example">    <p><b>Example #1 <b>levenshtein()</b> example</b></p>    <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;input&nbsp;misspelled&nbsp;word<br /></span><span style="color: #0000BB">$input&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'carrrot'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;array&nbsp;of&nbsp;words&nbsp;to&nbsp;check&nbsp;against<br /></span><span style="color: #0000BB">$words&nbsp;&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">'apple'</span><span style="color: #007700">,</span><span style="color: #DD0000">'pineapple'</span><span style="color: #007700">,</span><span style="color: #DD0000">'banana'</span><span style="color: #007700">,</span><span style="color: #DD0000">'orange'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'radish'</span><span style="color: #007700">,</span><span style="color: #DD0000">'carrot'</span><span style="color: #007700">,</span><span style="color: #DD0000">'pea'</span><span style="color: #007700">,</span><span style="color: #DD0000">'bean'</span><span style="color: #007700">,</span><span style="color: #DD0000">'potato'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;no&nbsp;shortest&nbsp;distance&nbsp;found,&nbsp;yet<br /></span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">=&nbsp;-</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;loop&nbsp;through&nbsp;words&nbsp;to&nbsp;find&nbsp;the&nbsp;closest<br /></span><span style="color: #007700">foreach&nbsp;(</span><span style="color: #0000BB">$words&nbsp;</span><span style="color: #007700">as&nbsp;</span><span style="color: #0000BB">$word</span><span style="color: #007700">)&nbsp;{<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;calculate&nbsp;the&nbsp;distance&nbsp;between&nbsp;the&nbsp;input&nbsp;word,<br />&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;and&nbsp;the&nbsp;current&nbsp;word<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$lev&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">levenshtein</span><span style="color: #007700">(</span><span style="color: #0000BB">$input</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$word</span><span style="color: #007700">);<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;check&nbsp;for&nbsp;an&nbsp;exact&nbsp;match<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$lev&nbsp;</span><span style="color: #007700">==&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">)&nbsp;{<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;closest&nbsp;word&nbsp;is&nbsp;this&nbsp;one&nbsp;(exact&nbsp;match)<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$closest&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$word</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">;<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;break&nbsp;out&nbsp;of&nbsp;the&nbsp;loop;&nbsp;we've&nbsp;found&nbsp;an&nbsp;exact&nbsp;match<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">break;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;if&nbsp;this&nbsp;distance&nbsp;is&nbsp;less&nbsp;than&nbsp;the&nbsp;next&nbsp;found&nbsp;shortest<br />&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;distance,&nbsp;OR&nbsp;if&nbsp;a&nbsp;next&nbsp;shortest&nbsp;word&nbsp;has&nbsp;not&nbsp;yet&nbsp;been&nbsp;found<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">if&nbsp;(</span><span style="color: #0000BB">$lev&nbsp;</span><span style="color: #007700">&lt;=&nbsp;</span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">||&nbsp;</span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">&lt;&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;set&nbsp;the&nbsp;closest&nbsp;match,&nbsp;and&nbsp;shortest&nbsp;distance<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$closest&nbsp;&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$word</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$lev</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br />echo&nbsp;</span><span style="color: #DD0000">"Input&nbsp;word:&nbsp;$input\n"</span><span style="color: #007700">;<br />if&nbsp;(</span><span style="color: #0000BB">$shortest&nbsp;</span><span style="color: #007700">==&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Exact&nbsp;match&nbsp;found:&nbsp;$closest\n"</span><span style="color: #007700">;<br />}&nbsp;else&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"Did&nbsp;you&nbsp;mean:&nbsp;$closest?\n"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">?&gt;</span></span></code></div>    </div>    <div class="example-contents"><p>The above example will output:</p></div>    <div class="example-contents"><pre><div class="cdata"><pre>Input word: carrrotDid you mean: carrot?</pre></div>    </pre></div>   </div>  </p> </div> <div class="refsect1 seealso">  <h3 class="title">See Also</h3>  <p class="para">   <ul class="simplelist">    <li class="member"><a href="function.soundex.html" class="function" rel="rdfs-seeAlso">soundex()</a></li>    <li class="member"><a href="function.similar-text.html" class="function" rel="rdfs-seeAlso">similar_text()</a></li>    <li class="member"><a href="function.metaphone.html" class="function" rel="rdfs-seeAlso">metaphone()</a></li>   </ul>  </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.lcfirst.html">lcfirst</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.localeconv.html">localeconv</a></div> <div class="up"><a href="ref.strings.html">String Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>

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