json_encode

(PHP 5 >= 5.2.0, PHP 7, PHP 8, PECL json >= 1.2.0)

json_encode对变量进行 JSON 编码

说明

json_encode(mixed $value, int $flags = 0, int $depth = 512): string|false

返回字符串,包含了 value 值 JSON 形式的表示。如果参数是 arrayobject,则会递归序列化。

如果要序列化的值是对象,则默认仅包含公开可见的属性,或者类可以实现 JsonSerializable 控制其值如何序列化为 JSON

编码受传入的 flags 参数影响,此外浮点值的编码依赖于 serialize_precision

参数

value

待编码的 value ,除了 resource 类型之外,可以为任何数据类型。

所有字符串数据的编码必须是 UTF-8。

注意:

PHP 实现了 JSON 的一个超集,参考 » RFC 7159.

flags

由以下常量组成的二进制掩码: JSON_FORCE_OBJECTJSON_HEX_QUOTJSON_HEX_TAGJSON_HEX_AMPJSON_HEX_APOSJSON_INVALID_UTF8_IGNOREJSON_INVALID_UTF8_SUBSTITUTEJSON_NUMERIC_CHECKJSON_PARTIAL_OUTPUT_ON_ERRORJSON_PRESERVE_ZERO_FRACTIONJSON_PRETTY_PRINTJSON_UNESCAPED_LINE_TERMINATORSJSON_UNESCAPED_SLASHESJSON_UNESCAPED_UNICODEJSON_THROW_ON_ERROR。 关于 JSON 常量详情参考 JSON 常量页面。

depth

设置最大深度。 必须大于0。

返回值

成功则返回 JSON 编码的 string 或者在失败时返回 false

更新日志

版本 说明
7.3.0 flags 参数新增 JSON_THROW_ON_ERROR 常量。
7.2.0 flags 参数新增 JSON_INVALID_UTF8_IGNOREJSON_INVALID_UTF8_SUBSTITUTE 常量。
7.1.0 flags 参数新增 JSON_UNESCAPED_LINE_TERMINATORS 常量。
7.1.0 float 值进行编码时,使用 serialize_precision 代替 precision

示例

示例 #1 json_encode() 例子

<?php
$arr
= array ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5);

echo
json_encode($arr);
?>

以上示例会输出:

{"a":1,"b":2,"c":3,"d":4,"e":5}

示例 #2 json_encode() 函数中 flags 参数的用法

<?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";
?>

以上示例会输出:

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"}

示例 #3 选项 JSON_NUMERIC_CHECK 例子

<?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)
);
?>

以上示例的输出类似于:

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"]"

示例 #4 连续与非连续数组示例

<?php
echo "连续数组".PHP_EOL;
$sequential = array("foo", "bar", "baz", "blong");
var_dump(
$sequential,
json_encode($sequential)
);

echo
PHP_EOL."非连续数组".PHP_EOL;
$nonsequential = array(1=>"foo", 2=>"bar", 3=>"baz", 4=>"blong");
var_dump(
$nonsequential,
json_encode($nonsequential)
);

echo
PHP_EOL."删除一个连续数组值的方式产生的非连续数组".PHP_EOL;
unset(
$sequential[1]);
var_dump(
$sequential,
json_encode($sequential)
);
?>

以上示例会输出:

连续数组
array(4) {
  [0]=>
  string(3) "foo"
  [1]=>
  string(3) "bar"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(27) "["foo","bar","baz","blong"]"

非连续数组
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"}"

删除一个连续数组值的方式产生的非连续数组
array(3) {
  [0]=>
  string(3) "foo"
  [2]=>
  string(3) "baz"
  [3]=>
  string(5) "blong"
}
string(33) "{"0":"foo","2":"baz","3":"blong"}"

示例 #5 选项 JSON_PRESERVE_ZERO_FRACTION 的例子

<?php
var_dump
(json_encode(12.0, JSON_PRESERVE_ZERO_FRACTION));
var_dump(json_encode(12.0));
?>

以上示例会输出:

string(4) "12.0"
string(2) "12"

注释

注意:

如果执行失败,可以通过 json_last_error() 函数来获取详细错误信息。

注意:

如果要编码的数组的键不是从0开始的数字,所有的键将会被当作字符串,并明确声明为 key-value 对。

注意:

参考 JSON 解析器,如果指定简单的 stringintegerfloatboolean 作为输入 valuejson_encode() 将生成简单的值的 JSON(既不是对象又不是数组)。虽然大多数解码器会接受这些值作为有效的 JSON,但有些可能不会,因为在这一点上规范是模棱两可的。

总而言之,应该测试下 JSON decoder 能否处理 json_encode() 生成的数据。

参见