json-encode.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.json-encode" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>json_encode</refname>
  <refpurpose>Returns the JSON representation of a value</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>string</type><type>false</type></type><methodname>json_encode</methodname>
   <methodparam><type>mixed</type><parameter>value</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>flags</parameter><initializer>0</initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>depth</parameter><initializer>512</initializer></methodparam>
  </methodsynopsis>
  <para>
   Returns a string containing the JSON representation of the supplied
   <parameter>value</parameter>.  If the parameter is an &array; or &object;,
   it will be serialized recursively.
  </para>
  <para>
   If a value to be serialized is an object, then by default only publicly visible
   properties will be included. Alternatively, a class may implement <interfacename>JsonSerializable</interfacename>
   to control how its values are serialized to <acronym>JSON</acronym>.
  </para>
  <para>
   The encoding is affected by the supplied <parameter>flags</parameter>
   and additionally the encoding of float values depends on the value of
   <link linkend="ini.serialize-precision">serialize_precision</link>.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>value</parameter></term>
     <listitem>
      <para>
       The <parameter>value</parameter> being encoded. Can be any type except
       a &resource;.
      </para>
      <para>
       All string data must be UTF-8 encoded.
      </para>
      &json.implementation.superset;
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>flags</parameter></term>
     <listitem>
      <para>
       Bitmask consisting of
       <constant>JSON_FORCE_OBJECT</constant>,
       <constant>JSON_HEX_QUOT</constant>,
       <constant>JSON_HEX_TAG</constant>,
       <constant>JSON_HEX_AMP</constant>,
       <constant>JSON_HEX_APOS</constant>,
       <constant>JSON_INVALID_UTF8_IGNORE</constant>,
       <constant>JSON_INVALID_UTF8_SUBSTITUTE</constant>,
       <constant>JSON_NUMERIC_CHECK</constant>,
       <constant>JSON_PARTIAL_OUTPUT_ON_ERROR</constant>,
       <constant>JSON_PRESERVE_ZERO_FRACTION</constant>,
       <constant>JSON_PRETTY_PRINT</constant>,
       <constant>JSON_UNESCAPED_LINE_TERMINATORS</constant>,
       <constant>JSON_UNESCAPED_SLASHES</constant>,
       <constant>JSON_UNESCAPED_UNICODE</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>
    <varlistentry>
     <term><parameter>depth</parameter></term>
     <listitem>
      <para>
       Set the maximum depth. Must be greater than zero.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns a JSON encoded &string; on success &return.falseforfailure;.
  </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>
        <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>
        <constant>JSON_UNESCAPED_LINE_TERMINATORS</constant>
        <parameter>flags</parameter> was added.
       </entry>
      </row>
      <row>
       <entry>7.1.0</entry>
       <entry>
        <link linkend="ini.serialize-precision">serialize_precision</link> is
        used instead of <link linkend="ini.precision">precision</link> when
        encoding <type>float</type> values.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>A <function>json_encode</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$arr = array('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5);

echo json_encode($arr);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
{"a":1,"b":2,"c":3,"d":4,"e":5}
]]>
    </screen>
   </example>

   <example>
    <title>
     A <function>json_encode</function> example showing some flags in use
    </title>
    <programlisting role="php">
<![CDATA[
<?php
$a = array('<foo>',"'bar'",'"baz"','&blong&', "\xc3\xa9");

echo "Normal: ",  json_encode($a), "\n";
echo "Tags: ",    json_encode($a, JSON_HEX_TAG), "\n";
echo "Apos: ",    json_encode($a, JSON_HEX_APOS), "\n";
echo "Quot: ",    json_encode($a, JSON_HEX_QUOT), "\n";
echo "Amp: ",     json_encode($a, JSON_HEX_AMP), "\n";
echo "Unicode: ", json_encode($a, JSON_UNESCAPED_UNICODE), "\n";
echo "All: ",     json_encode($a, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_QUOT | JSON_HEX_AMP | JSON_UNESCAPED_UNICODE), "\n\n";

$b = array();

echo "Empty array output as array: ", json_encode($b), "\n";
echo "Empty array output as object: ", json_encode($b, JSON_FORCE_OBJECT), "\n\n";

$c = array(array(1,2,3));

echo "Non-associative array output as array: ", json_encode($c), "\n";
echo "Non-associative array output as object: ", json_encode($c, JSON_FORCE_OBJECT), "\n\n";

$d = array('foo' => 'bar', 'baz' => 'long');

echo "Associative array always output as object: ", json_encode($d), "\n";
echo "Associative array always output as object: ", json_encode($d, JSON_FORCE_OBJECT), "\n\n";
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Normal: ["<foo>","'bar'","\"baz\"","&blong&","\u00e9"]
Tags: ["\u003Cfoo\u003E","'bar'","\"baz\"","&blong&","\u00e9"]
Apos: ["<foo>","\u0027bar\u0027","\"baz\"","&blong&","\u00e9"]
Quot: ["<foo>","'bar'","\u0022baz\u0022","&blong&","\u00e9"]
Amp: ["<foo>","'bar'","\"baz\"","\u0026blong\u0026","\u00e9"]
Unicode: ["<foo>","'bar'","\"baz\"","&blong&","é"]
All: ["\u003Cfoo\u003E","\u0027bar\u0027","\u0022baz\u0022","\u0026blong\u0026","é"]

Empty array output as array: []
Empty array output as object: {}

Non-associative array output as array: [[1,2,3]]
Non-associative array output as object: {"0":{"0":1,"1":2,"2":3}}

Associative array always output as object: {"foo":"bar","baz":"long"}
Associative array always output as object: {"foo":"bar","baz":"long"}
]]>
    </screen>
   </example>
   <example>
    <title>JSON_NUMERIC_CHECK option example</title>
    <programlisting role="php">
<![CDATA[
<?php
echo "Strings representing numbers automatically turned into numbers".PHP_EOL;
$numbers = array('+123123', '-123123', '1.2e3', '0.00001');
var_dump(
 $numbers,
 json_encode($numbers, JSON_NUMERIC_CHECK)
);
echo "Strings containing improperly formatted numbers".PHP_EOL;
$strings = array('+a33123456789', 'a123');
var_dump(
 $strings,
 json_encode($strings, JSON_NUMERIC_CHECK)
);
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Strings representing numbers automatically turned into numbers
array(4) {
  [0]=>
  string(7) "+123123"
  [1]=>
  string(7) "-123123"
  [2]=>
  string(5) "1.2e3"
  [3]=>
  string(7) "0.00001"
}
string(28) "[123123,-123123,1200,1.0e-5]"
Strings containing improperly formatted numbers
array(2) {
  [0]=>
  string(13) "+a33123456789"
  [1]=>
  string(4) "a123"
}
string(24) "["+a33123456789","a123"]"
]]>
    </screen>
   </example>
   <example>
    <title>Sequential versus non-sequential array example</title>
    <programlisting role="php">
<![CDATA[
<?php
echo "Sequential array".PHP_EOL;
$sequential = array("foo", "bar", "baz", "blong");
var_dump(
 $sequential,
 json_encode($sequential)
);

echo PHP_EOL."Non-sequential array".PHP_EOL;
$nonsequential = array(1=>"foo", 2=>"bar", 3=>"baz", 4=>"blong");
var_dump(
 $nonsequential,
 json_encode($nonsequential)
);

echo PHP_EOL."Sequential array with one key unset".PHP_EOL;
unset($sequential[1]);
var_dump(
 $sequential,
 json_encode($sequential)
);
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
Sequential array
array(4) {
  [0]=>
  string(3) "foo"
  [1]=>
  string(3) "bar"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(27) "["foo","bar","baz","blong"]"

Non-sequential array
array(4) {
  [1]=>
  string(3) "foo"
  [2]=>
  string(3) "bar"
  [3]=>
  string(3) "baz"
  [4]=>
  string(5) "blong"
}
string(43) "{"1":"foo","2":"bar","3":"baz","4":"blong"}"

Sequential array with one key unset
array(3) {
  [0]=>
  string(3) "foo"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(33) "{"0":"foo","2":"baz","3":"blong"}"
]]>
    </screen>
   </example>
   <example>
    <title><constant>JSON_PRESERVE_ZERO_FRACTION</constant> option example</title>
    <programlisting role="php">
<![CDATA[
<?php
var_dump(json_encode(12.0, JSON_PRESERVE_ZERO_FRACTION));
var_dump(json_encode(12.0));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
string(4) "12.0"
string(2) "12"
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    In the event of a failure to encode, <function>json_last_error</function>
    can be used to determine the exact nature of the error.
   </para>
  </note>
  <note>
   <para>
    When encoding an array, if the keys are not a continuous numeric
    sequence starting from 0, all keys are encoded as strings, and
    specified explicitly for each key-value pair.
   </para>
  </note>
  <note>
   <para>
    Like the reference JSON encoder, <function>json_encode</function> will
    generate JSON that is a simple value (that is, neither an object nor an
    array) if given a &string;, &integer;, &float; or &boolean; as an input
    <parameter>value</parameter>. While most decoders will accept these values
    as valid JSON, some may not, as the specification is ambiguous on this
    point.
   </para>
   <para>
    To summarise, always test that your JSON decoder can handle the output you
    generate from <function>json_encode</function>.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><interfacename>JsonSerializable</interfacename></member>
    <member><function>json_decode</function></member>
    <member><function>json_last_error</function></member>
    <member><function>json_last_error_msg</function></member>
    <member><function>serialize</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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