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

<refnamediv>

<refname>json_decode</refname>

<refpurpose>Decodes a JSON string</refpurpose>

</refnamediv>

<refsect1 role="description">

&reftitle.description;

<methodsynopsis>

<type>mixed</type><methodname>json_decode</methodname>

<methodparam><type>string</type><parameter>json</parameter></methodparam>

<methodparam choice="opt"><type class="union"><type>bool</type><type>null</type></type><parameter>associative</parameter><initializer>&null;</initializer></methodparam>

<methodparam choice="opt"><type>int</type><parameter>depth</parameter><initializer>512</initializer></methodparam>

<methodparam choice="opt"><type>int</type><parameter>flags</parameter><initializer>0</initializer></methodparam>

</methodsynopsis>

<para>

Takes a JSON encoded string and converts it into a PHP value.

</para>

</refsect1>

<refsect1 role="parameters">

&reftitle.parameters;

<para>

<variablelist>

<varlistentry>

<term><parameter>json</parameter></term>

<listitem>

<para>

The <parameter>json</parameter> <type>string</type> being decoded.

</para>

<para>

This function only works with UTF-8 encoded strings.

</para>

&json.implementation.superset;

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>associative</parameter></term>

<listitem>

<para>

When &true;, JSON objects will be returned as

associative &array;s; when &false;, JSON objects will be returned as &object;s.

When &null;, JSON objects will be returned as associative &array;s or

&object;s depending on whether <constant>JSON_OBJECT_AS_ARRAY</constant>

is set in the <parameter>flags</parameter>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>depth</parameter></term>

<listitem>

<para>

Maximum nesting depth of the structure being decoded.

The value must be greater than <literal>0</literal>,

and less than or equal to <literal>2147483647</literal>.

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>flags</parameter></term>

<listitem>

<para>

Bitmask of

<constant>JSON_BIGINT_AS_STRING</constant>,

<constant>JSON_INVALID_UTF8_IGNORE</constant>,

<constant>JSON_INVALID_UTF8_SUBSTITUTE</constant>,

<constant>JSON_OBJECT_AS_ARRAY</constant>,

<constant>JSON_THROW_ON_ERROR</constant>.

The behaviour of these constants is described on the

<link linkend="json.constants">JSON constants</link> page.

</para>

</listitem>

</varlistentry>

</variablelist>

</para>

</refsect1>

<refsect1 role="returnvalues">

&reftitle.returnvalues;

<para>

Returns the value encoded in <parameter>json</parameter> as an appropriate

PHP type. Unquoted values <literal>true</literal>, <literal>false</literal>

and <literal>null</literal> are returned as &true;,

&false; and &null; respectively. &null; is returned if the

<parameter>json</parameter> cannot be decoded or if the encoded data is

deeper than the nesting limit.

</para>

</refsect1>

<refsect1 role="errors">

&reftitle.errors;

<para>

If <parameter>depth</parameter> is outside the allowed range,

a <classname>ValueError</classname> is thrown as of PHP 8.0.0,

while previously, an error of level <constant>E_WARNING</constant> was raised.

</para>

</refsect1>

<refsect1 role="changelog">

&reftitle.changelog;

<para>

<informaltable>

<tgroup cols="2">

<thead>

<row>

<entry>&Version;</entry>

<entry>&Description;</entry>

</row>

</thead>

<tbody>

<row>

<entry>7.3.0</entry>

<entry>

<constant>JSON_THROW_ON_ERROR</constant>

<parameter>flags</parameter> was added.

</entry>

</row>

<row>

<entry>7.2.0</entry>

<entry>

<parameter>associative</parameter> is nullable now.

</entry>

</row>

<row>

<entry>7.2.0</entry>

<entry>

<constant>JSON_INVALID_UTF8_IGNORE</constant>, and

<constant>JSON_INVALID_UTF8_SUBSTITUTE</constant>

<parameter>flags</parameter> were added.

</entry>

</row>

<row>

<entry>7.1.0</entry>

<entry>

An empty JSON key ("") can be encoded to the empty object property

instead of using a key with value <literal>_empty_</literal>.

</entry>

</row>

</tbody>

</tgroup>

</informaltable>

</para>

</refsect1>

<refsect1 role="examples">

&reftitle.examples;

<para>

<example>

<title><function>json_decode</function> examples</title>

<programlisting role="php">

<![CDATA[

<?php

$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';

var_dump(json_decode($json));

var_dump(json_decode($json, true));

?>

]]>

</programlisting>

&example.outputs;

<screen>

<![CDATA[

object(stdClass)#1 (5) {

["a"] => int(1)

["b"] => int(2)

["c"] => int(3)

["d"] => int(4)

["e"] => int(5)

}

array(5) {

["a"] => int(1)

["b"] => int(2)

["c"] => int(3)

["d"] => int(4)

["e"] => int(5)

}

]]>

</screen>

</example>

<example>

<title>Accessing invalid object properties</title>

<simpara>

Accessing elements within an object that contain characters not

permitted under PHP's naming convention (e.g. the hyphen) can be

accomplished by encapsulating the element name within braces and the apostrophe.

</simpara>

<programlisting role="php">

<![CDATA[

<?php

$json = '{"foo-bar": 12345}';

$obj = json_decode($json);

print $obj->{'foo-bar'}; // 12345

?>

]]>

</programlisting>

</example>

<example>

<title>common mistakes using <function>json_decode</function></title>

<programlisting role="php">

<![CDATA[

<?php

// the following strings are valid JavaScript but not valid JSON

// the name and value must be enclosed in double quotes

// single quotes are not valid

$bad_json = "{ 'bar': 'baz' }";

json_decode($bad_json); // null

// the name must be enclosed in double quotes

$bad_json = '{ bar: "baz" }';

json_decode($bad_json); // null

// trailing commas are not allowed

$bad_json = '{ bar: "baz", }';

json_decode($bad_json); // null

?>

]]>

</programlisting>

</example>

<example>

<title><parameter>depth</parameter> errors</title>

<programlisting role="php">

<![CDATA[

<?php

// Encode some data with a maximum depth of 4 (array -> array -> array -> string)

$json = json_encode(

array(

1 => array(

'English' => array(

'One',

'January'

),

'French' => array(

'Une',

'Janvier'

)

)

)

);

// Show the errors for different depths.

var_dump(json_decode($json, true, 4));

echo 'Last error: ', json_last_error_msg(), PHP_EOL, PHP_EOL;

var_dump(json_decode($json, true, 3));

echo 'Last error: ', json_last_error_msg(), PHP_EOL, PHP_EOL;

?>

]]>

</programlisting>

&example.outputs;

<screen>

<![CDATA[

array(1) {

[1]=>

array(2) {

["English"]=>

array(2) {

[0]=>

string(3) "One"

[1]=>

string(7) "January"

}

["French"]=>

array(2) {

[0]=>

string(3) "Une"

[1]=>

string(7) "Janvier"

}

}

}

Last error: No error

NULL

Last error: Maximum stack depth exceeded

]]>

</screen>

</example>

<example>

<title><function>json_decode</function> of large integers</title>

<programlisting role="php">

<![CDATA[

<?php

$json = '{"number": 12345678901234567890}';

var_dump(json_decode($json));

var_dump(json_decode($json, false, 512, JSON_BIGINT_AS_STRING));

?>

]]>

</programlisting>

&example.outputs;

<screen>

<![CDATA[

object(stdClass)#1 (1) {

["number"]=>

float(1.2345678901235E+19)

}

object(stdClass)#1 (1) {

["number"]=>

string(20) "12345678901234567890"

}

]]>

</screen>

</example>

</para>

</refsect1>

<refsect1 role="notes">

&reftitle.notes;

<note>

<para>

The JSON spec is not JavaScript, but a subset of JavaScript.

</para>

</note>

<note>

<para>

In the event of a failure to decode, <function>json_last_error</function>

can be used to determine the exact nature of the error.

</para>

</note>

</refsect1>

<refsect1 role="seealso">

&reftitle.seealso;

<para>

<simplelist>

<member><function>json_encode</function></member>

<member><function>json_last_error</function></member>

</simplelist>

</para>

</refsect1>

</refentry>

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