function.sqlite-create-function.html
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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>Registers a "regular" User Defined Function for use in SQL statements</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.sqlite-create-aggregate.html">sqlite_create_aggregate</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.sqlite-current.html">sqlite_current</a></div> <div class="up"><a href="ref.sqlite.html">SQLite Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><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, PECL pdo_sqlite:0.2-0.3 sqlite:1.0-1.0.3)</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> <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><b>sqlite_create_function</b></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.html#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> ] )</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><b>createFunction</b></b></span> ( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$function_name</tt></span> , <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.callback" class="type callback">callback</a></span> <tt class="parameter">$callback</tt></span> [, <span class="methodparam"><span class="type">int</span> <tt class="parameter">$num_args</tt></span> ] )</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> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">dbhandle</tt></i></span> <dd> <p class="para"> The SQLite Database resource; returned from <a href="function.sqlite-open.html" class="function">sqlite_open()</a> when used procedurally. This parameter is not required when using the object-oriented method. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">function_name</tt></i></span> <dd> <p class="para"> The name of the function used in SQL statements. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">callback</tt></i></span> <dd> <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.html#language.types.intro" class="link">scalar type</a>). </span> </p></blockquote> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">num_args</tt></i></span> <dd> <p class="para"> Hint to the SQLite parser if the callback function accepts a predetermined number of arguments. </p> </dd> </dt> </dl> </p> <blockquote><p><b class="note">Note</b>: <span class="simpara">Two alternative syntaxes aresupported 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> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> No value is returned. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 <b>sqlite_create_function()</b> example</b></p> <div class="example-contents"><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">$sqliteerror</span><span style="color: #007700">;<br /> exit;<br />}<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> <p class="para"> In this example, we have a function that calculates the md5 sum of a string, and then reverses it. When the SQL statement executes, it returns the value of the filename transformed by our function. The data returned in <i><tt class="parameter">$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 foreach() 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"> <div class="example"> <p><b>Example #2 Example of using the PHP function</b></p> <div class="example-contents"><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"><p> This example will call the <a href="function.md5.html" 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> <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.html" class="function">sqlite_udf_encode_binary()</a> and <a href="function.sqlite-udf-decode-binary.html" 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.html" class="function">sqlite_create_aggregate()</a> to override SQLite native SQL functions. </p> </div> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.sqlite-create-aggregate.html" class="function" rel="rdfs-seeAlso">sqlite_create_aggregate()</a></li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.sqlite-create-aggregate.html">sqlite_create_aggregate</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.sqlite-current.html">sqlite_current</a></div> <div class="up"><a href="ref.sqlite.html">SQLite Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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