PHP: strcasecmp

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class="refpurpose"><span class="refname">strcasecmp</span> — <span class="dc-title">Binary safe case-insensitive string comparison</span></p> </div> <div class="refsect1 description" id="refsect1-function.strcasecmp-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="methodname"><strong>strcasecmp</strong></span>(<span class="methodparam"><span class="type"><a href="language.types.string.php" class="type string">string</a></span> <code class="parameter">$string1</code></span>, <span class="methodparam"><span class="type"><a href="language.types.string.php" class="type string">string</a></span> <code class="parameter">$string2</code></span>): <span class="type"><a href="language.types.integer.php" class="type int">int</a></span></div> <p class="para rdfs-comment"> Binary safe case-insensitive string comparison. The comparison is not locale aware; only ASCII letters are compared in a case-insensitive way. </p> </div> <div class="refsect1 parameters" id="refsect1-function.strcasecmp-parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt><code class="parameter">string1</code></dt> <dd> <p class="para"> The first string </p> </dd> <dt><code class="parameter">string2</code></dt> <dd> <p class="para"> The second string </p> </dd> </dl> </p> </div> <div class="refsect1 returnvalues" id="refsect1-function.strcasecmp-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns <code class="literal">-1</code> if <code class="parameter">string1</code> is less than <code class="parameter">string2</code>; <code class="literal">1</code> if <code class="parameter">string1</code> is greater than <code class="parameter">string2</code>, and <code class="literal">0</code> if they are equal. </p> </div> <div class="refsect1 changelog" id="refsect1-function.strcasecmp-changelog"> <h3 class="title">Changelog</h3> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>8.2.0</td> <td> This function now returns <code class="literal">-1</code> or <code class="literal">1</code>, where it previously returned a negative or positive number. </td> </tr> </tbody> </table> </div> <div class="refsect1 examples" id="refsect1-function.strcasecmp-examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example" id="example-5006"> <p><strong>Example #1 <span class="function"><strong>strcasecmp()</strong></span> example</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br />$var1 </span><span style="color: #007700">= </span><span style="color: #DD0000">"Hello"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$var2 </span><span style="color: #007700">= </span><span style="color: #DD0000">"hello"</span><span style="color: #007700">;<br />if (</span><span style="color: #0000BB">strcasecmp</span><span style="color: #007700">(</span><span style="color: #0000BB">$var1</span><span style="color: #007700">, </span><span style="color: #0000BB">$var2</span><span style="color: #007700">) == </span><span style="color: #0000BB">0</span><span style="color: #007700">) {<br /> echo </span><span style="color: #DD0000">'$var1 is equal to $var2 in a case-insensitive string comparison'</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> </div> <div class="refsect1 seealso" id="refsect1-function.strcasecmp-seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li><span class="function"><a href="function.strcmp.php" class="function" rel="rdfs-seeAlso">strcmp()</a> - Binary safe string comparison</span></li> <li><span class="function"><a href="function.preg-match.php" class="function" rel="rdfs-seeAlso">preg_match()</a> - Perform a regular expression match</span></li> <li><span class="function"><a href="function.substr-compare.php" class="function" rel="rdfs-seeAlso">substr_compare()</a> - Binary safe comparison of two strings from an offset, up to length characters</span></li> <li><span class="function"><a href="function.strncasecmp.php" class="function" rel="rdfs-seeAlso">strncasecmp()</a> - Binary safe case-insensitive string comparison of the first n characters</span></li> <li><span class="function"><a href="function.stristr.php" class="function" rel="rdfs-seeAlso">stristr()</a> - Case-insensitive strstr</span></li> <li><span class="function"><a href="function.substr.php" class="function" rel="rdfs-seeAlso">substr()</a> - Return part of a string</span></li> </ul> </p> </div> </div> <div class="contribute"> <h3 class="title">Found A Problem?</h3> <div> </div> <div class="edit-bug"> <a href="https://github.com/php/doc-base/blob/master/README.md" title="This will take you to our contribution guidelines on GitHub" target="_blank" rel="noopener noreferrer">Learn How To Improve This Page</a> • <a href="https://github.com/php/doc-en/blob/master/reference/strings/functions/strcasecmp.xml">Submit a Pull Request</a> • <a href="https://github.com/php/doc-en/issues/new?body=From%20manual%20page:%20https:%2F%2Fphp.net%2Ffunction.strcasecmp%0A%0A---">Report a Bug</a> </div> </div><section id="usernotes"> <div class="head"> <span class="action"><a href="/manual/add-note.php?sect=function.strcasecmp&repo=en&redirect=https://www.php.net/manual/en/function.strcasecmp.php">＋<small>add a note</small></a></span> <h3 class="title">User Contributed Notes <span class="count">4 notes</span></h3> </div><div id="allnotes"> <div class="note" id="107016"> <div class="votes"> <div id="Vu107016"> <a href="/manual/vote-note.php?id=107016&page=function.strcasecmp&vote=up" title="Vote up!" class="usernotes-voteu">up</a> </div> <div id="Vd107016"> <a href="/manual/vote-note.php?id=107016&page=function.strcasecmp&vote=down" title="Vote down!" class="usernotes-voted">down</a> </div> <div class="tally" id="V107016" title="64% like this..."> 28 </div> </div> <a href="#107016" class="name"> <strong class="user"><em>chris at cmbuckley dot co dot uk</em></strong></a><a class="genanchor" href="#107016"> ¶</a><div class="date" title="2011-12-28 04:59"><strong>12 years ago</strong></div> <div class="text" id="Hcom107016"> <div class="phpcode"><code><span class="html">A simple multibyte-safe case-insensitive string comparison:<br /><br /><span class="default"><?php<br /><br /></span><span class="keyword">function </span><span class="default">mb_strcasecmp</span><span class="keyword">(</span><span class="default">$str1</span><span class="keyword">, </span><span class="default">$str2</span><span class="keyword">, </span><span class="default">$encoding </span><span class="keyword">= </span><span class="default">null</span><span class="keyword">) {<br /> if (</span><span class="default">null </span><span class="keyword">=== </span><span class="default">$encoding</span><span class="keyword">) { </span><span class="default">$encoding </span><span class="keyword">= </span><span class="default">mb_internal_encoding</span><span class="keyword">(); }<br /> return </span><span class="default">strcmp</span><span class="keyword">(</span><span class="default">mb_strtoupper</span><span class="keyword">(</span><span class="default">$str1</span><span class="keyword">, </span><span class="default">$encoding</span><span class="keyword">), </span><span class="default">mb_strtoupper</span><span class="keyword">(</span><span class="default">$str2</span><span class="keyword">, </span><span class="default">$encoding</span><span class="keyword">));<br />}<br /><br /></span><span class="default">?><br /></span><br />Caveat: watch out for edge cases like "ß".</span></code></div> </div> </div> <div class="note" id="123230"> <div class="votes"> <div id="Vu123230"> <a href="/manual/vote-note.php?id=123230&page=function.strcasecmp&vote=up" title="Vote up!" class="usernotes-voteu">up</a> </div> <div id="Vd123230"> <a href="/manual/vote-note.php?id=123230&page=function.strcasecmp&vote=down" title="Vote down!" class="usernotes-voted">down</a> </div> <div class="tally" id="V123230" title="71% like this..."> 20 </div> </div> <a href="#123230" class="name"> <strong class="user"><em>chrislarham at NOSPAM dot outlook dot com</em></strong></a><a class="genanchor" href="#123230"> ¶</a><div class="date" title="2018-10-13 08:47"><strong>6 years ago</strong></div> <div class="text" id="Hcom123230"> <div class="phpcode"><code><span class="html">I didn't see any explanation in the documentation as to precisely how the positive/negative return values are calculated for unequal strings.<br /><br />After a bit of experimentation it appears that it's the difference in alphabetical position of the first character in unequal strings.<br /><br />For example, the letter 'z' is the 26th letter while the letter 'a' is the 1st letter:<br /><br /><span class="default"><?php<br /><br /> $zappl </span><span class="keyword">= </span><span class="string">"zappl"</span><span class="keyword">;<br /> </span><span class="default">$apple </span><span class="keyword">= </span><span class="string">"apple"</span><span class="keyword">;<br /><br /> echo </span><span class="default">strcasecmp</span><span class="keyword">(</span><span class="default">$zappl</span><span class="keyword">, </span><span class="default">$apple</span><span class="keyword">); </span><span class="comment">#outputs 25 [26 - 1]<br /> </span><span class="keyword">echo </span><span class="default">strcasecmp</span><span class="keyword">(</span><span class="default">$apple</span><span class="keyword">, </span><span class="default">$zappl</span><span class="keyword">); </span><span class="comment">#outputs -25 [1 - 26]<br /><br /></span><span class="default">?><br /></span><br />This might be incredibly obvious to most people, but hopefully it will clarify the calculation process for some others.</span></code></div> </div> </div> <div class="note" id="24729"> <div class="votes"> <div id="Vu24729"> <a href="/manual/vote-note.php?id=24729&page=function.strcasecmp&vote=up" title="Vote up!" class="usernotes-voteu">up</a> </div> <div id="Vd24729"> <a href="/manual/vote-note.php?id=24729&page=function.strcasecmp&vote=down" title="Vote down!" class="usernotes-voted">down</a> </div> <div class="tally" id="V24729" title="57% like this..."> 9 </div> </div> <a href="#24729" class="name"><strong class="user"><em>Anonymous</em></strong></a><a class="genanchor" href="#24729"> ¶</a><div class="date" title="2002-08-27 06:53"><strong>22 years ago</strong></div> <div class="text" id="Hcom24729"> <div class="phpcode"><code><span class="html">The sample above is only true on some platforms that only use a simple 'C' locale, where individual bytes are considered as complete characters that are converted to lowercase before being differentiated.<br /><br />Other locales (see LC_COLLATE and LC_ALL) use the difference of collation order of characters, where characters may be groups of bytes taken from the input strings, or simply return -1, 0, or 1 as the collation order is not simply defined by comparing individual characters but by more complex rules.<br /><br />Don't base your code on a specific non null value returned by strcmp() or strcasecmp(): it is not portable. Just consider the sign of the result and be sure to use the correct locale!</span></code></div> </div> </div> <div class="note" id="99128"> <div class="votes"> <div id="Vu99128"> <a href="/manual/vote-note.php?id=99128&page=function.strcasecmp&vote=up" title="Vote up!" class="usernotes-voteu">up</a> </div> <div id="Vd99128"> <a href="/manual/vote-note.php?id=99128&page=function.strcasecmp&vote=down" title="Vote down!" class="usernotes-voted">down</a> </div> <div class="tally" id="V99128" title="54% like this..."> 4 </div> </div> <a href="#99128" class="name"> <strong class="user"><em>alvaro at demogracia dot com</em></strong></a><a class="genanchor" href="#99128"> ¶</a><div class="date" title="2010-07-29 05:35"><strong>14 years ago</strong></div> <div class="text" id="Hcom99128"> <div class="phpcode"><code><span class="html">Don't forget this is a single-byte function: in Unicode strings it'll provide incoherent results as soon as both strings differ only in case. There doesn't seem to exist a built-in multi-byte alternative so you need to write your own, taking into account both character encoding and collation.</span></code></div> </div> </div></div> <div class="foot"><a href="/manual/add-note.php?sect=function.strcasecmp&repo=en&redirect=https://www.php.net/manual/en/function.strcasecmp.php">＋<small>add a note</small></a></div> </section> </section> <aside class='layout-menu'> <ul class='parent-menu-list'> <li> <a href="ref.strings.php">String Functions</a> <ul class='child-menu-list'> <li class=""> <a href="function.addcslashes.php" title="addcslashes">addcslashes</a> </li> <li class=""> <a href="function.addslashes.php" title="addslashes">addslashes</a> </li> <li class=""> <a href="function.bin2hex.php" title="bin2hex">bin2hex</a> </li> <li class=""> <a href="function.chop.php" title="chop">chop</a> </li> <li class=""> <a href="function.chr.php" title="chr">chr</a> </li> <li class=""> <a href="function.chunk-split.php" 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