(PHP 5 >= 5.2.0, PECL json >= 1.2.0)
json_decode — 对 JSON 格式的字符串进行编码
$json
[, bool $assoc = false
[, int $depth = 512
[, int $options = 0
]]] )接受一个 JSON 格式的字符串并且把它转换为 PHP 变量
Returns the value encoded in json in appropriate
PHP type. Values true, false and
null (case-insensitive) are returned as TRUE, FALSE
and NULL respectively. NULL is returned if the
json cannot be decoded or if the encoded
data is deeper than the recursion limit.
Example #1 json_decode() 的例子
<?php
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));
var_dump(json_decode($json, true));
?>
以上例程会输出：
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)
}
Example #2 Accessing invalid object properties
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.
<?php
$json = '{"foo-bar": 12345}';
$obj = json_decode($json);
print $obj->{'foo-bar'}; // 12345
?>
Example #3 common mistakes using json_decode()
<?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
?>
Example #4 depth errors
<?php
// Encode the data.
$json = json_encode(
array(
1 => array(
'English' => array(
'One',
'January'
),
'French' => array(
'Une',
'Janvier'
)
)
)
);
// Define the errors.
$constants = get_defined_constants(true);
$json_errors = array();
foreach ($constants["json"] as $name => $value) {
if (!strncmp($name, "JSON_ERROR_", 11)) {
$json_errors[$value] = $name;
}
}
// Show the errors for different depths.
foreach (range(4, 3, -1) as $depth) {
var_dump(json_decode($json, true, $depth));
echo 'Last error: ', $json_errors[json_last_error()], PHP_EOL, PHP_EOL;
}
?>
以上例程会输出：
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: JSON_ERROR_NONE
NULL
Last error: JSON_ERROR_DEPTH
Example #5 json_decode() of large integers
<?php
$json = '12345678901234567890';
var_dump(json_decode($json));
var_dump(json_decode($json, false, 512, JSON_BIGINT_AS_STRING));
?>
以上例程会输出：
float(1.2345678901235E+19) string(20) "12345678901234567890"
Note:
The JSON spec is not JavaScript, but a subset of JavaScript.
Note:
In the event of a failure to decode, json_last_error() can be used to determine the exact nature of the error.
| 版本 | 说明 |
|---|---|
| 5.4.0 |
The options parameter was added.
|
| 5.3.0 | Added the optional depth. The default recursion depth was increased from 128 to 512 |
| 5.2.3 | The nesting limit was increased from 20 to 128 |
| 5.2.1 | Added support for JSON decoding of basic types. |