mirror of
https://github.com/sigmasternchen/php-doc-en
synced 2025-03-20 19:08:54 +00:00
028513e94b
Also, simplify the first paragraph of 'Traditional assertions' in assert() docs git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@342126 c90b9560-bf6c-de11-be94-00142212c4b1
277 lines
7 KiB
XML
277 lines
7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
|
|
<!-- $Revision$ -->
|
|
<refentry xml:id="function.create-function" xmlns="http://docbook.org/ns/docbook">
|
|
<refnamediv>
|
|
<refname>create_function</refname>
|
|
<refpurpose>Create an anonymous (lambda-style) function</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
&warn.deprecated.function-7-2-0;
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1 role="description">
|
|
&reftitle.description;
|
|
<methodsynopsis>
|
|
<type>string</type><methodname>create_function</methodname>
|
|
<methodparam><type>string</type><parameter>args</parameter></methodparam>
|
|
<methodparam><type>string</type><parameter>code</parameter></methodparam>
|
|
</methodsynopsis>
|
|
<para>
|
|
Creates an anonymous function from the parameters passed, and
|
|
returns a unique name for it.
|
|
</para>
|
|
<caution>
|
|
<para>
|
|
This function internally performs an <function>eval</function> and as such has the
|
|
same security issues as <function>eval</function>. Additionally it has bad performance
|
|
and memory usage characteristics.
|
|
</para>
|
|
<para>
|
|
If you are using PHP 5.3.0 or newer a native
|
|
<link linkend="functions.anonymous">anonymous function</link> should be used instead.
|
|
</para>
|
|
</caution>
|
|
</refsect1>
|
|
<refsect1 role="parameters">
|
|
&reftitle.parameters;
|
|
<para>
|
|
Usually these parameters will be passed as single quote delimited strings.
|
|
The reason for using single quoted strings, is to protect the variable
|
|
names from parsing, otherwise, if you use double quotes there will be a
|
|
need to escape the variable names, e.g. <literal>\$avar</literal>.
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><parameter>args</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
The function arguments.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
<varlistentry>
|
|
<term><parameter>code</parameter></term>
|
|
<listitem>
|
|
<para>
|
|
The function code.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 role="returnvalues">
|
|
&reftitle.returnvalues;
|
|
<para>
|
|
Returns a unique function name as a string, or &false; on error.
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 role="examples">
|
|
&reftitle.examples;
|
|
<para>
|
|
<example>
|
|
<title>
|
|
Creating an anonymous function with <function>create_function</function>
|
|
</title>
|
|
<para>
|
|
You can use this function, to (for example) create a function from
|
|
information gathered at run time:
|
|
</para>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
$newfunc = create_function('$a,$b', 'return "ln($a) + ln($b) = " . log($a * $b);');
|
|
echo "New anonymous function: $newfunc\n";
|
|
echo $newfunc(2, M_E) . "\n";
|
|
// outputs
|
|
// New anonymous function: lambda_1
|
|
// ln(2) + ln(2.718281828459) = 1.6931471805599
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
Or, perhaps to have general handler function that can apply a set
|
|
of operations to a list of parameters:
|
|
</para>
|
|
<para>
|
|
<example>
|
|
<title>
|
|
Making a general processing function with
|
|
<function>create_function</function>
|
|
</title>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
function process($var1, $var2, $farr)
|
|
{
|
|
foreach ($farr as $f) {
|
|
echo $f($var1, $var2) . "\n";
|
|
}
|
|
}
|
|
|
|
// create a bunch of math functions
|
|
$f1 = 'if ($a >=0) {return "b*a^2 = ".$b*sqrt($a);} else {return false;}';
|
|
$f2 = "return \"min(b^2+a, a^2,b) = \".min(\$a*\$a+\$b,\$b*\$b+\$a);";
|
|
$f3 = 'if ($a > 0 && $b != 0) {return "ln(a)/b = ".log($a)/$b; } else { return false; }';
|
|
$farr = array(
|
|
create_function('$x,$y', 'return "some trig: ".(sin($x) + $x*cos($y));'),
|
|
create_function('$x,$y', 'return "a hypotenuse: ".sqrt($x*$x + $y*$y);'),
|
|
create_function('$a,$b', $f1),
|
|
create_function('$a,$b', $f2),
|
|
create_function('$a,$b', $f3)
|
|
);
|
|
|
|
echo "\nUsing the first array of anonymous functions\n";
|
|
echo "parameters: 2.3445, M_PI\n";
|
|
process(2.3445, M_PI, $farr);
|
|
|
|
// now make a bunch of string processing functions
|
|
$garr = array(
|
|
create_function('$b,$a', 'if (strncmp($a, $b, 3) == 0) return "** \"$a\" '.
|
|
'and \"$b\"\n** Look the same to me! (looking at the first 3 chars)";'),
|
|
create_function('$a,$b', '; return "CRCs: " . crc32($a) . ", ".crc32($b);'),
|
|
create_function('$a,$b', '; return "similar(a,b) = " . similar_text($a, $b, &$p) . "($p%)";')
|
|
);
|
|
echo "\nUsing the second array of anonymous functions\n";
|
|
process("Twas brilling and the slithy toves", "Twas the night", $garr);
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
&example.outputs;
|
|
<screen>
|
|
<![CDATA[
|
|
Using the first array of anonymous functions
|
|
parameters: 2.3445, M_PI
|
|
some trig: -1.6291725057799
|
|
a hypotenuse: 3.9199852871011
|
|
b*a^2 = 4.8103313314525
|
|
min(b^2+a, a^2,b) = 8.6382729035898
|
|
ln(a)/b = 0.27122299212594
|
|
|
|
Using the second array of anonymous functions
|
|
** "Twas the night" and "Twas brilling and the slithy toves"
|
|
** Look the same to me! (looking at the first 3 chars)
|
|
CRCs: -725381282, 342550513
|
|
similar(a,b) = 11(45.833333333333%)
|
|
]]>
|
|
</screen>
|
|
</example>
|
|
</para>
|
|
<para>
|
|
But perhaps the most common use for of lambda-style (anonymous) functions
|
|
is to create callback functions, for example when using
|
|
<function>array_walk</function> or <function>usort</function>
|
|
</para>
|
|
<para>
|
|
<example>
|
|
<title>Using anonymous functions as callback functions</title>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
$av = array("the ", "a ", "that ", "this ");
|
|
array_walk($av, create_function('&$v,$k', '$v = $v . "mango";'));
|
|
print_r($av);
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
&example.outputs;
|
|
<screen>
|
|
<![CDATA[
|
|
Array
|
|
(
|
|
[0] => the mango
|
|
[1] => a mango
|
|
[2] => that mango
|
|
[3] => this mango
|
|
)
|
|
]]>
|
|
</screen>
|
|
<para>
|
|
an array of strings ordered from shorter to longer
|
|
</para>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
|
|
$sv = array("small", "larger", "a big string", "it is a string thing");
|
|
print_r($sv);
|
|
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
&example.outputs;
|
|
<screen>
|
|
<![CDATA[
|
|
Array
|
|
(
|
|
[0] => small
|
|
[1] => larger
|
|
[2] => a big string
|
|
[3] => it is a string thing
|
|
)
|
|
]]>
|
|
</screen>
|
|
<para>
|
|
sort it from longer to shorter
|
|
</para>
|
|
<programlisting role="php">
|
|
<![CDATA[
|
|
<?php
|
|
|
|
usort($sv, create_function('$a,$b','return strlen($b) - strlen($a);'));
|
|
print_r($sv);
|
|
|
|
?>
|
|
]]>
|
|
</programlisting>
|
|
&example.outputs;
|
|
<screen>
|
|
<![CDATA[
|
|
Array
|
|
(
|
|
[0] => it is a string thing
|
|
[1] => a big string
|
|
[2] => larger
|
|
[3] => small
|
|
)
|
|
]]>
|
|
</screen>
|
|
</example>
|
|
</para>
|
|
</refsect1>
|
|
|
|
<refsect1 role="seealso">
|
|
&reftitle.seealso;
|
|
<para>
|
|
<simplelist>
|
|
<member><link linkend="functions.anonymous">Anonymous functions</link></member>
|
|
</simplelist>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|
|
|
|
<!-- Keep this comment at the end of the file
|
|
Local variables:
|
|
mode: sgml
|
|
sgml-omittag:t
|
|
sgml-shorttag:t
|
|
sgml-minimize-attributes:nil
|
|
sgml-always-quote-attributes:t
|
|
sgml-indent-step:1
|
|
sgml-indent-data:t
|
|
indent-tabs-mode:nil
|
|
sgml-parent-document:nil
|
|
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
|
|
sgml-exposed-tags:nil
|
|
sgml-local-catalogs:nil
|
|
sgml-local-ecat-files:nil
|
|
End:
|
|
vim600: syn=xml fen fdm=syntax fdl=2 si
|
|
vim: et tw=78 syn=sgml
|
|
vi: ts=1 sw=1
|
|
-->
|