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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.json-validate" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>json_validate</refname>
<refpurpose>Checks if a string contains valid JSON</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>bool</type><methodname>json_validate</methodname>
<methodparam><type>string</type><parameter>json</parameter></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>
Returns whether the given &string; is syntactically valid JSON.
If <function>json_validate</function> returns &true;, <function>json_decode</function>
will successfully decode the given string when using the same
<parameter>depth</parameter> and <parameter>flags</parameter>.
</para>
<para>
If <function>json_validate</function> returns &false;, the cause
can be retrieved using <function>json_last_error</function> and
<function>json_last_error_msg</function>.
</para>
<para>
<function>json_validate</function> uses less memory than
<function>json_decode</function> if the decoded JSON payload is
not used, because it does not need to build the array or
object structure containing the payload.
</para>
<caution>
<para>
Calling <function>json_validate</function> immediately before
<function>json_decode</function> will unnecessarily parse the string
twice, as <function>json_decode</function> implicitly performs
validation during decoding.
</para>
<para>
<function>json_validate</function> should therefore only be used
if the decode JSON payload is not immediately used and knowing whether
the string contains valid JSON is needed.
</para>
</caution>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>json</parameter></term>
<listitem>
<para>
The string to validate.
</para>
<para>
This function only works with UTF-8 encoded strings.
</para>
&json.implementation.superset;
</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>
Currently only
<constant>JSON_INVALID_UTF8_IGNORE</constant>
is accepted.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns &true; if the given string is syntactically valid JSON, otherwise
returns &false;.
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
If <parameter>depth</parameter> is outside the allowed range,
a <classname>ValueError</classname> is thrown.
</para>
<para>
If <parameter>flags</parameter> is not a valid flag,
a <classname>ValueError</classname> is thrown.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>json_validate</function> examples</title>
<programlisting role="php">
<![CDATA[
<?php
var_dump(json_validate('{ "test": { "foo": "bar" } }'));
var_dump(json_validate('{ "": "": "" } }'));
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
bool(true)
bool(false)
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>json_decode</function></member>
<member><function>json_last_error</function></member>
<member><function>json_last_error_msg</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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