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<title>Function Overloading Feature</title>
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<h1>
Function Overloading Feature
</h1>
<p class="para">
You might often find it difficult to get an existing PHP application
to work in a given multibyte environment. This happens because most
PHP applications out there are written with the standard string
functions such as <span class="function"><a href="function.substr.html" class="function">substr()</a></span>, which are known to
not properly handle multibyte-encoded strings.
</p>
<p class="para">
mbstring supports a 'function overloading' feature which enables
you to add multibyte awareness to such an application without
code modification by overloading multibyte counterparts on
the standard string functions. For example,
<span class="function"><a href="function.mb-substr.html" class="function">mb_substr()</a></span> is called instead of
<span class="function"><a href="function.substr.html" class="function">substr()</a></span> if function overloading is enabled.
This feature makes it easy to port applications that only support
single-byte encodings to a multibyte environment in many cases.
</p>
<p class="para">
To use function overloading, set
<em>mbstring.func_overload</em> in <var class="filename">php.ini</var> to a
positive value that represents a combination of bitmasks specifying
the categories of functions to be overloaded. It should be set
to 1 to overload the <span class="function"><a href="function.mail.html" class="function">mail()</a></span> function. 2 for string
functions, 4 for regular expression functions. For example,
if it is set to 7, mail, strings and regular expression functions will
be overloaded. The list of overloaded functions are shown below.
<table class="doctable table">
<caption><strong>Functions to be overloaded</strong></caption>
<thead>
<tr>
<th>value of mbstring.func_overload</th>
<th>original function</th>
<th>overloaded function</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>1</td>
<td> <span class="function"><a href="function.mail.html" class="function">mail()</a></span></td>
<td> <span class="function"><a href="function.mb-send-mail.html" class="function">mb_send_mail()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strlen.html" class="function">strlen()</a></span></td>
<td> <span class="function"><a href="function.mb-strlen.html" class="function">mb_strlen()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strpos.html" class="function">strpos()</a></span></td>
<td> <span class="function"><a href="function.mb-strpos.html" class="function">mb_strpos()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strrpos.html" class="function">strrpos()</a></span></td>
<td> <span class="function"><a href="function.mb-strrpos.html" class="function">mb_strrpos()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.substr.html" class="function">substr()</a></span></td>
<td> <span class="function"><a href="function.mb-substr.html" class="function">mb_substr()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strtolower.html" class="function">strtolower()</a></span></td>
<td> <span class="function"><a href="function.mb-strtolower.html" class="function">mb_strtolower()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strtoupper.html" class="function">strtoupper()</a></span></td>
<td> <span class="function"><a href="function.mb-strtoupper.html" class="function">mb_strtoupper()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.stripos.html" class="function">stripos()</a></span></td>
<td> <span class="function"><a href="function.mb-stripos.html" class="function">mb_stripos()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strripos.html" class="function">strripos()</a></span></td>
<td> <span class="function"><a href="function.mb-strripos.html" class="function">mb_strripos()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strstr.html" class="function">strstr()</a></span></td>
<td> <span class="function"><a href="function.mb-strstr.html" class="function">mb_strstr()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.stristr.html" class="function">stristr()</a></span></td>
<td> <span class="function"><a href="function.mb-stristr.html" class="function">mb_stristr()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.strrchr.html" class="function">strrchr()</a></span></td>
<td> <span class="function"><a href="function.mb-strrchr.html" class="function">mb_strrchr()</a></span></td>
</tr>
<tr>
<td>2</td>
<td> <span class="function"><a href="function.substr-count.html" class="function">substr_count()</a></span></td>
<td> <span class="function"><a href="function.mb-substr-count.html" class="function">mb_substr_count()</a></span></td>
</tr>
<tr>
<td>4</td>
<td> <span class="function"><a href="function.ereg.html" class="function">ereg()</a></span></td>
<td> <span class="function"><a href="function.mb-ereg.html" class="function">mb_ereg()</a></span></td>
</tr>
<tr>
<td>4</td>
<td> <span class="function"><a href="function.eregi.html" class="function">eregi()</a></span></td>
<td> <span class="function"><a href="function.mb-eregi.html" class="function">mb_eregi()</a></span></td>
</tr>
<tr>
<td>4</td>
<td> <span class="function"><a href="function.ereg-replace.html" class="function">ereg_replace()</a></span></td>
<td> <span class="function"><a href="function.mb-ereg-replace.html" class="function">mb_ereg_replace()</a></span></td>
</tr>
<tr>
<td>4</td>
<td> <span class="function"><a href="function.eregi-replace.html" class="function">eregi_replace()</a></span></td>
<td> <span class="function"><a href="function.mb-eregi-replace.html" class="function">mb_eregi_replace()</a></span></td>
</tr>
<tr>
<td>4</td>
<td> <span class="function"><a href="function.split.html" class="function">split()</a></span></td>
<td> <span class="function"><a href="function.mb-split.html" class="function">mb_split()</a></span></td>
</tr>
</tbody>
</table>
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
It is not recommended to use the function overloading option in
the per-directory context, because it's not confirmed yet to be
stable enough in a production environment and may lead to undefined
behaviour.
</p>
</p></blockquote>
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