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<refentry xml:id="function.constant" xmlns="http://docbook.org/ns/docbook">

<refnamediv>

<refname>constant</refname>

<refpurpose>Returns the value of a constant</refpurpose>

</refnamediv>

<refsect1 role="description">

&reftitle.description;

<methodsynopsis>

<type>mixed</type><methodname>constant</methodname>

<methodparam><type>string</type><parameter>name</parameter></methodparam>

</methodsynopsis>

<simpara>

Return the value of the constant indicated by

<parameter>name</parameter>.

</simpara>

<simpara>

<function>constant</function> is useful if you need to retrieve

the value of a constant, but do not know its name. I.e. it is

stored in a variable or returned by a function.

</simpara>

<simpara>

This function works also with <link

linkend="language.oop5.constants">class constants</link> and <link

linkend="language.types.enumerations">enum cases</link>.

</simpara>

</refsect1>

<refsect1 role="parameters">

&reftitle.parameters;

<para>

<variablelist>

<varlistentry>

<term><parameter>name</parameter></term>

<listitem>

<para>

The constant name.

</para>

</listitem>

</varlistentry>

</variablelist>

</para>

</refsect1>

<refsect1 role="returnvalues">

&reftitle.returnvalues;

<para>

Returns the value of the constant.

</para>

</refsect1>

<refsect1 role="errors">

&reftitle.errors;

<para>

If the constant is not defined, an <classname>Error</classname> exception is thrown.

Prior to PHP 8.0.0, an <constant>E_WARNING</constant> level error was generated in that case.

</para>

</refsect1>

<refsect1 role="changelog">

&reftitle.changelog;

<informaltable>

<tgroup cols="2">

<thead>

<row>

<entry>&Version;</entry>

<entry>&Description;</entry>

</row>

</thead>

<tbody>

<row>

<entry>8.0.0</entry>

<entry>

If the constant is not defined, <function>constant</function> now throws an

<classname>Error</classname> exception; previously an <constant>E_WARNING</constant>

was generated, and &null; was returned.

</entry>

</row>

</tbody>

</tgroup>

</informaltable>

</refsect1>

<refsect1 role="examples">

&reftitle.examples;

<para>

<example>

<title>Using <function>constant</function> with Constants</title>

<programlisting role="php">

<![CDATA[

<?php

define("MAXSIZE", 100);

echo MAXSIZE;

echo constant("MAXSIZE"); // same thing as the previous line

interface bar {

const test = 'foobar!';

}

class foo {

const test = 'foobar!';

}

$const = 'test';

var_dump(constant('bar::'. $const)); // string(7) "foobar!"

var_dump(constant('foo::'. $const)); // string(7) "foobar!"

?>

]]>

</programlisting>

</example>

<example>

<title>Using <function>constant</function> with Enum Cases (as of PHP 8.1.0)</title>

<programlisting role="php">

<![CDATA[

<?php

enum Suit

{

case Hearts;

case Diamonds;

case Clubs;

case Spades;

}

$case = 'Hearts';

var_dump(constant('Suit::'. $case)); // enum(Suit::Hearts)

?>

]]>

</programlisting>

</example>

</para>

</refsect1>

<refsect1 role="seealso">

&reftitle.seealso;

<para>

<simplelist>

<member><function>define</function></member>

<member><function>defined</function></member>

<member><function>get_defined_constants</function></member>

<member>The section on <link linkend="language.constants">Constants</link></member>

</simplelist>

</para>

</refsect1>

</refentry>

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