(PHP 5 >= 5.2.0, PHP 7, PHP 8, PECL json >= 1.2.0)
json_encode — 値を JSON 形式にして返す
与えられた value を JSON 形式にした文字列を返します。
引数が配列やオブジェクトの場合は、JSON 形式に再帰的に変換されます。
変換される値がオブジェクトの場合、 デフォルトでは public としてアクセス可能なプロパティのみが含まれます。 それ以外のやり方で、値を JSON 形式に変換する方法は、 JsonSerializable を実装することで制御できます。
エンコーディングは、flags の指定によって影響を受けます。
さらに、浮動小数点のエンコーディングは、
serialize_precision
の値によっても影響を受けます。
valueエンコードする値。 リソース 型以外の任意の型を指定できます。
すべての文字列データは、UTF-8 エンコードされていなければいけません。
注意:
PHP の実装は、 » RFC 7159 の JSON のスーパーセットです。
flags
JSON_FORCE_OBJECT,
JSON_HEX_QUOT,
JSON_HEX_TAG,
JSON_HEX_AMP,
JSON_HEX_APOS,
JSON_INVALID_UTF8_IGNORE,
JSON_INVALID_UTF8_SUBSTITUTE,
JSON_NUMERIC_CHECK,
JSON_PARTIAL_OUTPUT_ON_ERROR,
JSON_PRESERVE_ZERO_FRACTION,
JSON_PRETTY_PRINT,
JSON_UNESCAPED_LINE_TERMINATORS,
JSON_UNESCAPED_SLASHES,
JSON_UNESCAPED_UNICODE,
JSON_THROW_ON_ERROR
からなるビットマスク。
各定数の意味については
JSON 定数のページ
に説明があります。
depth最大の深さを設定します。正の数でなければいけません。
成功した場合に、JSON エンコードされた文字列を返します。
失敗した場合に false を返します。
| バージョン | 説明 |
|---|---|
| 7.3.0 |
flags パラメータに
JSON_THROW_ON_ERROR が追加されました。
|
| 7.2.0 |
flags パラメータに
JSON_INVALID_UTF8_IGNORE と
JSON_INVALID_UTF8_SUBSTITUTE が追加されました。
|
| 7.1.0 |
flags パラメータに
JSON_UNESCAPED_LINE_TERMINATORS が追加されました。
|
| 7.1.0 | float 値をエンコードする際に、 precision ではなく serialize_precision を使うようになりました。 |
例1 json_encode() の例
<?php
$arr = array('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5);
echo json_encode($arr);
?>上の例の出力は以下となります。
{"a":1,"b":2,"c":3,"d":4,"e":5}
例2 json_encode() で、利用中のいくつかのフラグを表示する例
<?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";
?>上の例の出力は以下となります。
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&","e"]
All: ["\u003Cfoo\u003E","\u0027bar\u0027","\u0022baz\u0022","\u0026blong\u0026","e"]
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"}
例3 JSON_NUMERIC_CHECK の例
<?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)
);
?>上の例の出力は、 たとえば以下のようになります。
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"]"
例4 シーケンシャルな配列とそうでない配列の例
<?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)
);
?>上の例の出力は以下となります。
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"}"
例5 JSON_PRESERVE_ZERO_FRACTION の例
<?php
var_dump(json_encode(12.0, JSON_PRESERVE_ZERO_FRACTION));
var_dump(json_encode(12.0));
?>上の例の出力は以下となります。
string(4) "12.0" string(2) "12"
注意:
エンコードに失敗した場合は、json_last_error() を使ってエラーの内容を調べることができます。
注意:
配列をエンコードする場合、もし配列のキーが 0 からはじまる連続した数値でなければ、 すべてのキーを文字列としてエンコードします。 そして、個々のキー/値のペアを明示的に指定します。
注意:
JSON エンコーダーのリファレンス実装と同様、 string や int、 float そして bool を入力として渡したときに json_encode() が生成する JSON はシンプルな値 (オブジェクトでもないし配列でもないもの) となります。 大半のエンコーダーはこういった値を妥当な JSON として扱いますが、中にはそうでないものもあります。 そのため、現時点ではこの仕様は不明瞭です。
要するに、json_encode() で生成した JSON が、あなたの使おうとしているデコーダーでデコードできるかどうかを常に確認する必要があるということです。
Are you sure you want to use JSON_NUMERIC_CHECK, really really sure?
Just watch this usecase:
<?php
// International phone number
json_encode(array('phone_number' => '+33123456789'), JSON_NUMERIC_CHECK);
?>
And then you get this JSON:
{"phone_number":33123456789}
Maybe it makes sense for PHP (as is_numeric('+33123456789') returns true), but really, casting it as an int?!
So be careful when using JSON_NUMERIC_CHECK, it may mess up with your data!Notice that JSON_FORCE_OBJECT will convert all non-associative arrays to objects. This is not necessarily a good solution for empty arrays.
If you want to convert only empty arrays to objects, simply convert them to empty object before use json_encode function.
For example:
<?php
$foo=array(
'empty2object'=>(object)[],
'empty2array'=>[],
);
echo json_encode($foo); // {"empty2object":{},"empty2array":[]}
?>Attention when passing a plain array to json_encode and using JSON_FORCE_OBJECT. It figured out that the index-order of the resulting JSON-string depends on the system PHP is running on.
$a = array("a" , "b", "c");
echo json_encode($a, JSON_FORCE_OBJECT);
On Xampp (Windows) you get:
{"0":"a","1":"b","2":"c"}';
On a machine running debian I get:
{"2":"a","1":"b","0":"c"}';
Note that the key:value pairs are different!
Solution here was to use array_combine to create a ssociative array and then pass it to json_encode:
json_encode(array_combine(range(0, count($a) - 1), $a), JSON_FORCE_OBJECT);Be careful with floating values in some locales (e.g. russian) with comma (",") as decimal point. Code:
<?php
setlocale(LC_ALL, 'ru_RU.utf8');
$arr = array('element' => 12.34);
echo json_encode( $arr );
?>
Output will be:
--------------
{"element":12,34}
--------------
Which is NOT a valid JSON markup. You should convert floating point variable to strings or set locale to something like "LC_NUMERIC, 'en_US.utf8'" before using json_encode.I came across the "bug" where running json_encode() over a SimpleXML object was ignoring the CDATA. I ran across http://bugs.php.net/42001 and http://bugs.php.net/41976, and while I agree with the poster that the documentation should clarify gotchas like this, I was able to figure out how to workaround it.
You need to convert the SimpleXML object back into an XML string, then re-import it back into SimpleXML using the LIBXML_NOCDATA option. Once you do this, then you can use json_encode() and still get back the CDATA.
<?php
// Pretend we already have a complex SimpleXML object stored in $xml
$json = json_encode(new SimpleXMLElement($xml->asXML(), LIBXML_NOCDATA));
?>A note about json_encode automatically quoting numbers:
It appears that the json_encode function pays attention to the data type of the value. Let me explain what we came across:
We have found that when retrieving data from our database, there are occasions when numbers appear as strings to json_encode which results in double quotes around the values.
This can lead to problems within javascript functions expecting the values to be numeric.
This was discovered when were were retrieving fields from the database which contained serialized arrays. After unserializing them and sending them through the json_encode function the numeric values in the original array were now being treated as strings and showing up with double quotes around them.
The fix: Prior to encoding the array, send it to a function which checks for numeric types and casts accordingly. Encoding from then on worked as expected.Beware of Trailing Backslashes!
The JSON specification *does not allow* trailing backslashes in strings. It will create a JSON-encoded string without throwing an error, but this string will cause an error when parsed.
For example, the string "Example\" will cause the following error in JavaScript when parsing:
JSON.parse: expected ',' or '}' after property value in object
This appears to be an oversight in the JSON specification and the only work-around appears to be removing trailing slashes from all strings before encoding.The Problem:
---------------
When you filter an array in PHP using array_filter, the original keys are preserved. If you remove elements, you'll end up with gaps in the keys (non-consecutive). When encoded to JSON, this can lead to the list being interpreted as a JSON object instead of a JSON array, which might not be what your JavaScript code expects.
The Solution:
---------------
The array_values() function is essential in this scenario. It re-indexes the array with consecutive numerical keys (0, 1, 2, ...), ensuring that the JSON output is always a well-formed array.
Example:
----------
<?php
// Use Case: Filtering a list and ensuring consistent JSON array output
// Imagine you have a list of items and need to send a filtered version to a JavaScript frontend
// using JSON. You want to ensure the filtered list is always received as a JSON array,
// regardless of which items were removed.
// Sample data: A list of items
$items = [
"first",
"second",
"third",
"fourth",
"fifth"
];
// Items to remove from the list
$itemsToRemove = ["second", "fourth"];
// Filter the list, keeping original keys (which become non-consecutive)
$filteredItems = array_filter($items, function($item) use ($itemsToRemove) {
return !in_array($item, $itemsToRemove);
});
// Prepare data for JSON output
$output_arr = [
"list" => $filteredItems
];
// Output 1: JSON with non-consecutive keys (becomes an object)
echo "Output without array_values:\n";
echo json_encode($output_arr, JSON_PRETTY_PRINT) . "\n\n";
/* Output:
{
"list": {
"0": "first",
"2": "third",
"4": "fifth"
}
}
*/
// Reset keys to be consecutive using array_values
$output_arr['list'] = array_values($output_arr['list']);
// Output 2: JSON with consecutive keys (remains an array)
echo "Output with array_values:\n";
echo json_encode($output_arr, JSON_PRETTY_PRINT) . "\n";
/* Output:
{
"list": [
"first",
"third",
"fifth"
]
}
*/
?>Solution for UTF-8 Special Chars.
<?
$array = array('nome'=>'Paição','cidade'=>'São Paulo');
$array = array_map('htmlentities',$array);
//encode
$json = html_entity_decode(json_encode($array));
//Output: {"nome":"Paição","cidade":"São Paulo"}
echo $json;
?>Note that if you try to encode an array containing non-utf values, you'll get null values in the resulting JSON string. You can batch-encode all the elements of an array with the array_map function:
<?php
$encodedArray = array_map(utf8_encode, $rawArray);
?>If you need pretty-printed output, but want it indented by 2 spaces instead of 4:
$json_indented_by_4 = json_encode($output, JSON_UNESCAPED_SLASHES|JSON_PRETTY_PRINT);
$json_indented_by_2 = preg_replace('/^( +?)\\1(?=[^ ])/m', '$1', $json_indented_by_4);