Source of: /manual/en/function.sqlite-create-function.php
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<div id="function.sqlite-create-function" class="refentry">
<div class="refnamediv">
<h1 class="refname">sqlite_create_function</h1>
<h1 class="refname">SQLiteDatabase->createFunction</h1>
<p class="verinfo">(PHP 5, sqlite >= 1.0.0)</p><p class="refpurpose"><span class="refname">sqlite_create_function</span> -- <span class="refname">SQLiteDatabase->createFunction</span> — <span class="dc-title">
Registers a "regular" User Defined Function for use in SQL statements
</span></p>
</div>
<a name="function.sqlite-create-function.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span> <span class="methodname"><b>sqlite_create_function</b></span>
( <span class="methodparam"><span class="type">resource</span> <tt class="parameter">$dbhandle</tt></span>
, <span class="methodparam"><span class="type">string</span> <tt class="parameter">$function_name</tt></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.php#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$callback</tt></span>
[, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$num_args</tt><span class="initializer"> = -1</span></span>
] )</div>
<p class="para rdfs-comment">Object oriented style (method):</p>
<div class="classsynopsis">
<div class="ooclass"><b class="classname">SQLiteDatabase</b></div>
<div class="methodsynopsis dc-description">
<span class="type">void</span> <span class="methodname"><b>createFunction</b></span>
( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$function_name</tt></span>
, <span class="methodparam"><span class="type"><a href="language.pseudo-types.php#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$callback</tt></span>
[, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$num_args</tt><span class="initializer"> = -1</span></span>
] )</div>
</div>
<p class="para">
<b>sqlite_create_function()</b> allows you to register a PHP
function with SQLite as an <acronym title="User Defined Functions">UDF</acronym> (User Defined
Function), so that it can be called from within your SQL statements.
</p>
<p class="para">
The UDF can be used in any SQL statement that can call functions, such as
SELECT and UPDATE statements and also in triggers.
</p>
</div>
<a name="function.sqlite-create-function.parameters"></a><div class="refsect1 parameters">
<h3 class="title">Parameters</h3>
<p class="para">
</p><dl>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">dbhandle</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The SQLite Database resource; returned from <a href="function.sqlite-open.php" class="function">sqlite_open()</a>
when used procedurally. This parameter is not required
when using the object-oriented method.
</p>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">function_name</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The name of the function used in SQL statements.
</p>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">callback</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
Callback function to handle the defined SQL function.
</p>
<blockquote><p><b class="note">Note</b>:
<span class="simpara">
Callback functions should return a type understood by SQLite (i.e.
<a href="language.types.intro.php" class="link">scalar type</a>).
</span>
</p></blockquote>
</dd>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">num_args</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
Hint to the SQLite parser if the callback function accepts a
predetermined number of arguments.
</p>
</dd>
</dl>
<p>
</p>
<blockquote><p><b class="note">Note</b>: <span class="simpara">Two alternative syntaxes are
supported for compatibility with other database extensions (such as MySQL).
The preferred form is the first, where the <i><tt class="parameter">dbhandle</tt></i>
parameter is the first parameter to the function.</span></p></blockquote>
</div>
<a name="function.sqlite-create-function.returnvalues"></a><div class="refsect1 returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
No value is returned.
</p>
</div>
<a name="function.sqlite-create-function.examples"></a><div class="refsect1 examples">
<h3 class="title">Examples</h3>
<p class="para">
</p><div class="example">
<p><b>Example #1 <b>sqlite_create_function()</b> example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">md5_and_reverse</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">) <br />{<br /> return </span><span style="color: #0000BB">strrev</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">));<br />}<br /><br />if (</span><span style="color: #0000BB">$dbhandle </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_open</span><span style="color: #007700">(</span><span style="color: #DD0000">'mysqlitedb'</span><span style="color: #007700">, </span><span style="color: #0000BB">0666</span><span style="color: #007700">, </span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">)) {<br /> <br /> </span><span style="color: #0000BB">sqlite_create_function</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #DD0000">'md5rev'</span><span style="color: #007700">, </span><span style="color: #DD0000">'md5_and_reverse'</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /> <br /> </span><span style="color: #0000BB">$sql </span><span style="color: #007700">= </span><span style="color: #DD0000">'SELECT md5rev(filename) FROM files'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$rows </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #0000BB">$sql</span><span style="color: #007700">);<br />} else {<br /> echo </span><span style="color: #DD0000">'Error opening sqlite db: ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">;<br /> exit;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div><p>
</p>
<p class="para">
In this example, we have a function that calculates the md5 sum of a
string, and then reverses it. When the SQL statement executes, it
returns the value of the filename transformed by our function. The data
returned in <i><tt class="parameter">$rows</tt></i>
contains the processed result.
</p>
<p class="para">
The beauty of this technique is that you do not need to process the
result using a <a href="control-structures.foreach.php" class="link">foreach</a> loop after you have queried for the data.
</p>
<p class="para">
PHP registers a special function named <i>php</i> when the
database is first opened. The php function can be used to call any PHP
function without having to register it first.
</p>
<p class="para">
</p><div class="example">
<p><b>Example #2 Example of using the PHP function</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$rows </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #DD0000">"SELECT php('md5', filename) from files"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents para"><p>
This example will call the <a href="function.md5.php" class="function">md5()</a> on each
<i>filename</i> column in the database and return the result
into <i><tt class="parameter">$rows</tt></i>
</p></div>
</div><p>
</p>
<blockquote><p><b class="note">Note</b>:
For performance reasons, PHP will not automatically encode/decode binary
data passed to and from your UDF's. You need to manually encode/decode
the parameters and return values if you need to process binary data in
this way. Take a look at <a href="function.sqlite-udf-encode-binary.php" class="function">sqlite_udf_encode_binary()</a>
and <a href="function.sqlite-udf-decode-binary.php" class="function">sqlite_udf_decode_binary()</a> for more details.
<br />
</p></blockquote>
<div class="tip"><b class="tip">Tip</b>
<p class="para">
It is not recommended to use UDF's to handle processing of
binary data, unless high performance is not a key requirement of your
application.
</p>
</div>
<div class="tip"><b class="tip">Tip</b>
<p class="para">
You can use <b>sqlite_create_function()</b> and
<a href="function.sqlite-create-aggregate.php" class="function">sqlite_create_aggregate()</a> to override SQLite native
SQL functions.
</p>
</div>
</div>
<a name="function.sqlite-create-function.seealso"></a><div class="refsect1 seealso">
<h3 class="title">See Also</h3>
<p class="para">
</p><ul class="simplelist">
<li class="member"><a href="function.sqlite-create-aggregate.php" class="function" rel="rdfs-seeAlso">sqlite_create_aggregate()</a> - Register an aggregating UDF for use in SQL statements</li>
</ul><p>
</p>
</div>
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