本篇文章主要介绍php中json的使用技巧及实例，感兴趣的朋友参考下，希望对大家有所帮助。
一、json_encode()
该函数主要用来将数组和对象，转换为json格式。先看一个数组转换的例子：
$arr = array ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5);echo json_encode($arr);
结果为
{"a":1,"b":2,"c":3,"d":4,"e":5}
再看一个对象转换的例子：
$obj->body = 'another post';$obj->id = 21;$obj->approved = true;$obj->favorite_count = 1;$obj->status = null;echo json_encode($obj);
结果为
{"body":"another post",　"id":21,"approved":true,"favorite_count":1,"status":null}
由于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。当中文使用gb2312编码，或者外文使用iso-8859-1编码的时候，这一点要特别注意。
二、索引数组和关联数组
php支持两种数组，一种是只保存"值"（value）的索引数组（indexed array），另一种是保存"名值对"（name/value）的关联数组（associative array）。
由于javascript不支持关联数组，所以json_encode()只将索引数组（indexed array）转为数组格式，而将关联数组（associative array）转为对象格式。
比如，现在有一个索引数组
$arr = array('one', 'two', 'three');echo json_encode($arr);
结果为：
["one","two","three"]
如果将它改为关联数组：
$arr = array('1'=>'one', '2'=>'two', '3'=>'three');echo json_encode($arr);
结果就变了：
{"1":"one","2":"two","3":"three"}
注意，数据格式从"[]"（数组）变成了"{}"（对象）。
如果你需要将"索引数组"强制转化成"对象"，可以这样写
json_encode( (object)$arr );
或者
json_encode ( $arr, json_force_object );
三、类（class）的转换
下面是一个php的类：
class foo {const error_code = '404';public $public_ex = 'this is public';private $private_ex = 'this is private!';protected $protected_ex = 'this should be protected';public function geterrorcode() {return self::error_code;}}
现在，对这个类的实例进行json转换：
$foo = new foo;$foo_json = json_encode($foo);echo $foo_json;
输出结果是
{"public_ex":"this is public"}
可以看到，除了公开变量（public），其他东西（常量、私有变量、方法等等）都遗失了。
四、json_decode()
该函数用于将json文本转换为相应的php数据结构。下面是一个例子：
$json = '{"foo": 12345}';$obj = json_decode($json);　print $obj->{'foo'}; // 12345
通常情况下，json_decode()总是返回一个php对象，而不是数组。比如：
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';var_dump(json_decode($json));
结果就是生成一个php对象：
object(stdclass)#1 (5) {["a"] => int(1)["b"] => int(2)["c"] => int(3)["d"] => int(4)["e"] => int(5)}
如果想要强制生成php关联数组，json_decode()需要加一个参数true：
$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';var_dump(json_decode($json,true));
结果就生成了一个关联数组：
array(5) { ["a"] => int(1) ["b"] => int(2) ["c"] => int(3) ["d"] => int(4) ["e"] => int(5)}　
五、json_decode()的常见错误
下面三种json写法都是错的，你能看出错在哪里吗？
$bad_json = "{ 'bar': 'baz' }";$bad_json = '{ bar: "baz" }';$bad_json = '{ "bar": "baz", }';
对这三个字符串执行json_decode()都将返回null，并且报错。
第一个的错误是，json的分隔符（delimiter）只允许使用双引号，不能使用单引号。第二个的错误是，json名值对的"名"（冒号左边的部分），任何情况下都必须使用双引号。第三个的错误是，最后一个值之后不能添加逗号（trailing comma）。
另外，json只能用来表示对象（object）和数组（array），如果对一个字符串或数值使用json_decode()，将会返回null。
var_dump(json_decode("hello world")); //null
下面给大家介绍哦php语言的json实现
由于开发一个ajax file manager for web开源项目,数据交换使用的json格式，后来发现在低版本的php上运行会有问题，仔细调试发现json_decode和json_encode无法正常工作，于是查阅资料，发现低版本的php没有实现这两个函数，为了兼容性，我只好自己实现一个php版的json编码解码代码，并保证和json2.js的一致，测试调试并通过，现在将其公布出来，供有相同需求的同学使用：
<?php /* * **************************************************************************** * $base: $ * * $author: $ * berlin qin * * $history: base.js $ * berlin qin // created * * $contacted * webfmt@gmail.com * www.webfmt.com * * *************************************************************************** */ /* =========================================================================== * license * * 、open source licenses * webfmt is distributed under the gpl, lgpl and mpl open source licenses. * this triple copyleft licensing model avoids incompatibility with other open source licenses. * these open source licenses are specially indicated for: * integrating webfmt into open source software; * personal and educational use of webfmt; * integrating webfmt in commercial software, * taking care of satisfying the open source licenses terms, * while not able or interested on supporting webfmt and its development. * * 、commercial license – fbis source closed distribution license - cdl * for many companies and products, open source licenses are not an option. * this is why the fbis source closed distribution license (cdl) has been introduced. * it is a non-copyleft license which gives companies complete freedom * when integrating webfmt into their products and web sites. * this license offers a very flexible way to integrate webfmt in your commercial application. * these are the main advantages it offers over an open source license: * modifications and enhancements doesn't need to be released under an open source license; * there is no need to distribute any open source license terms alongside with your product * and no reference to it have to be done; * no references to webfmt have to be done in any file distributed with your product; * the source code of webfmt doesn't have to be distributed alongside with your product; * you can remove any file from webfmt when integrating it with your product. * the cdl is a lifetime license valid for all releases of webfmt published during * and before the year following its purchase. * it's valid for webfmt releases also. it includes year of personal e-mail support. * * ************************************************************************************************************************************************* */ function jsondecode($json) { $result = array(); try { if (php_version_id > ) { $result = (array) json_decode($json); } else { $json = str_replace(array("\\\\", "\\\""), array("", ""), $json); $parts = preg_split("@(\"[^\"]*\")|([\[\]\{\},:])|\s@is", $json, -, preg_split_no_empty | preg_split_delim_capture); foreach ($parts as $index => $part) { if (strlen($part) == ) { switch ($part) { case "[": case "{": $parts[$index] = "array("; break; case "]": case "}": $parts[$index] = ")"; break; case ":": $parts[$index] = "=>"; break; case ",": break; default: break; } } } $json = str_replace(array("", "", "$"), array("\\\\", "\\\"", "\\$"), implode("", $parts)); $result = eval("return $json;"); } } catch (exception $e) { $result = array("error" => $e->getcode()); } return $result; } function valuetostr($val) { if (is_string($val)) { $val = str_replace('\"', "\\\"", $val); $val = str_replace("\\", "\\\\", $val); $val = str_replace("/", "\\/", $val); $val = str_replace("\t", "\\t", $val); $val = str_replace("\n", "\\n", $val); $val = str_replace("\r", "\\r", $val); $val = str_replace("\b", "\\b", $val); $val = str_replace("\f", "\\f", $val); return '"' . $val . '"'; } elseif (is_int($val)) return sprintf('%d', $val); elseif (is_float($val)) return sprintf('%f', $val); elseif (is_bool($val)) return ($val ? 'true' : 'false'); else return 'null'; } function jsonencode($arr) { $result = "{}"; try { if (php_version_id > ) { $result = json_encode($arr); } else { $parts = array(); $is_list = false; if (!is_array($arr)) { $arr = (array) $arr; } $end = count($arr) - ; if (count($arr) > ) { if (is_numeric(key($arr))) { $result = "["; for ($i = ; $i < count($arr); $i++) { if (is_array($arr[$i])) { $result = $result . jsonencode($arr[$i]); } else { $result = $result . valuetostr($arr[$i]); } if ($i != $end) { $result = $result . ","; } } $result = $result . "]"; } else { $result = "{"; $i = ; foreach ($arr as $key => $value) { $result = $result . '"' . $key . '":'; if (is_array($value)) { $result = $result . jsonencode($value); } else { $result = $result . valuetostr($value); } if ($i != $end) { $result = $result . ","; } $i++; } $result = $result . "}"; } } else { $result = "[]"; } } } catch (exception $e) { } return $result; } ?>
总结：以上就是本篇文的全部内容，希望能对大家的学习有所帮助。
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以上就是php中json的使用技巧及实例的详细内容。