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php中json_decode()和json_encode()的使用方法

2019年04月17日  | 移动技术网IT编程  | 我要评论

1.json_decode()

json_decode
(php 5 >= 5.2.0, pecl json >= 1.2.0)

json_decode — 对 json 格式的字符串进行编码

说明
mixed json_decode ( string $json [, bool $assoc ] )
接受一个 json 格式的字符串并且把它转换为 php 变量

参数

json
待解码的 json string 格式的字符串。

assoc
当该参数为 true 时，将返回 array 而非 object 。


返回值
returns an object or if the optional assoc parameter is true, an associative array is instead returned.

范例

example #1 json_decode() 的例子

复制代码 代码如下:

<?php
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));
var_dump(json_decode($json, true));
?>

上例将输出：
复制代码 代码如下:

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)
}

复制代码 代码如下:

$data='[{"name":"a1","number":"123","contno":"000","qqno":""},{"name":"a1","number":"123","contno":"000","qqno":""},{"name":"a1","number":"123","contno":"000","qqno":""}]';
echo json_decode($data);

结果为：
复制代码 代码如下:

array ( [0] => stdclass object ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) [1] => stdclass object ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) [2] => stdclass object ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) )

可以看出经过json_decode()编译出来的是对象,现在输出json_decode($data,true)试下
复制代码 代码如下:

echo json_decode($data,true);

结果：
复制代码 代码如下:

array ( [0] => array ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) [1] => array ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) [2] => array ( [name] => a1 [number] => 123 [contno] => 000 [qqno] => ) )

可以看出 json_decode($data,true)输出的一个关联数组,由此可知json_decode($data）输出的是对象,而json_decode("$arr",true)是把它强制生成php关联数组.

2.json_encode()

json_encode
(php 5 >= 5.2.0, pecl json >= 1.2.0)

json_encode — 对变量进行 json 编码

report a bug 说明
string json_encode ( mixed $value [, int $options = 0 ] )
返回 value 值的 json 形式

report a bug 参数

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

该函数只能接受 utf-8 编码的数据

options
由以下常量组成的二进制掩码： json_hex_quot, json_hex_tag, json_hex_amp, json_hex_apos, json_numeric_check, json_pretty_print, json_unescaped_slashes, json_force_object, json_unescaped_unicode.

report a bug 返回值
编码成功则返回一个以 json 形式表示的 string 或者在失败时返回 false 。

report a bug 更新日志
版本 说明
5.4.0 options 参数增加常量： json_pretty_print, json_unescaped_slashes, 和 json_unescaped_unicode。
5.3.3 options 参数增加常量：json_numeric_check。
5.3.0 增加 options 参数.


report a bug 范例

example #1 a json_encode() 的例子
复制代码 代码如下:

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

echo json_encode($arr);
?>

以上例程会输出：
复制代码 代码如下:

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

example #2 json_encode() 函数中 options 参数的用法
复制代码 代码如下:

<?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";
?>

以上例程会输出：
复制代码 代码如下:

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"}

example #3 连续与非连续数组示例
复制代码 代码如下:

<?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)
);
?>

以上例程会输出：
复制代码 代码如下:

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"}"

复制代码 代码如下:

$obj->name= 'a1';$obj->number ='123';
$obj->contno= '000';
echo json_encode($obj);

结果为：
复制代码 代码如下:

{"name":"a1",
"number":"123",
"contno":"000"
}

可以看出json_encode()和json_decode()是编译和反编译过程，注意json只接受utf-8编码的字符，所以json_encode()的参数必须是utf-8编码，否则会得到空字符或者null。

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