关于 json 这个问题，陆陆续续有新手朋友找我问，比如为什么我输出的是 {1:item1,2:item2,3:item3} 而不是 [item1,item2,item3] 。 php数组 与 js数组 我这里用 php 5.4 以上语法表示。 php 里有关联数组和索引数组，例如： ?php // 索引数组 $arr = [ item1
关于 json 这个问题，陆陆续续有新手朋友找我问，比如为什么我输出的是 {"1":"item1","2":"item2","3":"item3"} 而不是 ["item1","item2","item3"]。
我这里用 php 5.4 以上语法表示。
php 里有关联数组和索引数组，例如：
<code class="sourceCode php"><span class="kw"><?php</span> <span class="co">// 索引数组</span> <span class="kw">$arr</span> = <span class="ot">[</span><span class="st">'item1'</span><span class="ot">,</span> <span class="st">'item2'</span><span class="ot">,</span> <span class="st">'item3'</span><span class="ot">];</span> <span class="co">// 关联数组</span> <span class="kw">$arr</span> = <span class="ot">[</span> <span class="st">'name'</span> => <span class="st">'张三'</span><span class="ot">,</span> <span class="st">'age'</span> => <span class="st">'22'</span><span class="ot">,</span> <span class="ot">];</span></code>
而 js 里只有一种数组，那就是索引数组，也许你会说可以用 K/V 键值对形式模拟关联数组啊。
K/V 键值对看起来像，但他没有任何数组特性，这里就不详细说明了。
而上面的 php 数组 json_encode 后得到的 json 格式分别是 ["item1","item2","item3"] 和 {"name":"\u5f20\u4e09","age":"22"}。这里的中文被转为 Unicode 了，如果你非要显示中文，php 5.4 之后支持 JSON_UNESCAPED_UNICODE 参数，json_encode($arr, JSON_UNESCAPED_UNICODE) 即可得到 {"name":"张三","age":"22"}，不过非常不推荐这样写。
这里分别得到的是 js 下的 数组 和 对象 格式的 json 字符串，那为什么会生成这两种类型，或者说，什么情况会生成对象格式，什么情况会生成数组格式呢。
大致几种情况我都列出来了，直接看代码。
<code class="sourceCode php"><span class="kw"><?php</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 不是 0 开始，会输出对象</span>
<span class="dv">1</span> => <span class="st">'item1'</span><span class="ot">,</span>
<span class="dv">2</span> => <span class="st">'item2'</span><span class="ot">,</span>
<span class="dv">3</span> => <span class="st">'item3'</span><span class="ot">,</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"输出对象: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 输出对象: {"1":"item1","2":"item2","3":"item3"}</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 连续索引，输出数组</span>
<span class="dv">0</span> => <span class="st">'item1'</span><span class="ot">,</span>
<span class="dv">1</span> => <span class="st">'item2'</span><span class="ot">,</span>
<span class="dv">2</span> => <span class="st">'item3'</span><span class="ot">,</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"输出数组: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 输出数组: ["item1","item2","item3"]</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 连续索引，输出数组 </span>
<span class="st">'item1'</span><span class="ot">,</span>
<span class="st">'item2'</span><span class="ot">,</span>
<span class="st">'item3'</span><span class="ot">,</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"输出数组: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 输出数组: ["item1","item2","item3"]</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 索引不连续，输出对象</span>
<span class="dv">0</span> => <span class="st">'item1'</span><span class="ot">,</span>
<span class="dv">1</span> => <span class="st">'item2'</span><span class="ot">,</span>
<span class="dv">2</span> => <span class="st">'item3'</span><span class="ot">,</span>
<span class="dv">5</span> => <span class="st">'item5'</span><span class="ot">,</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"输出对象: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 输出对象: {"0":"item1","1":"item2","2":"item3","5":"item5"}</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 包含关联索引，一定输出对象</span>
<span class="dv">0</span> => <span class="st">'item1'</span><span class="ot">,</span>
<span class="dv">1</span> => <span class="st">'item2'</span><span class="ot">,</span>
<span class="dv">2</span> => <span class="st">'item3'</span><span class="ot">,</span>
<span class="st">'other'</span> => <span class="st">'其他字段'</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"输出对象: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 输出对象: {"0":"item1","1":"item2","2":"item3","other":"\u5176\u4ed6\u5b57\u6bb5"}</span>
<span class="co">// 关联数组 + 索引数组 实例</span>
<span class="kw">$arr</span> = <span class="ot">[</span> <span class="co">// 关联数组</span>
<span class="st">'other'</span> => <span class="st">'其他字段'</span><span class="ot">,</span>
<span class="st">'count'</span> => <span class="dv">3</span><span class="ot">,</span> <span class="co">// 数组个数</span>
<span class="st">'list'</span> => <span class="ot">[</span> <span class="co">// 索引数组</span>
<span class="st">'item1'</span><span class="ot">,</span>
<span class="st">'item2'</span><span class="ot">,</span>
<span class="st">'item3'</span><span class="ot">,</span>
<span class="ot">],</span>
<span class="ot">];</span>
<span class="fu">echo</span> <span class="st">"对象+数组: "</span><span class="ot">,</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">),</span> <span class="st">"</span><span class="kw">\n</span><span class="st">"</span><span class="ot">;</span>
<span class="co">// 对象+数组: {"other":"\u5176\u4ed6\u5b57\u6bb5","count":3,"list":["item1","item2","item3"]}</span></code>其实第一种就是很多新手朋友经常遇到的问题。
因为数据库读出来后他们喜欢把 id 当索引用，而数据库的 id 不是从 0 开始的，看下这个例子。
<code class="sourceCode php"><span class="kw">$arr</span> = <span class="kw">$User</span>->where<span class="ot">(</span><span class="kw">$where</span><span class="ot">)</span>->find<span class="ot">();</span> <span class="co">// 读取数据</span>
<span class="kw">$list</span> = <span class="ot">[];</span>
<span class="kw">foreach</span><span class="ot">(</span><span class="kw">$arr</span> <span class="kw">as</span> <span class="kw">$key</span> => <span class="kw">$val</span><span class="ot">)</span> { <span class="co">// 遍历数组</span>
<span class="kw">$list</span><span class="ot">[</span><span class="kw">$key</span><span class="ot">]</span> = <span class="ot">[</span>
<span class="st">'name'</span> => <span class="kw">$val</span><span class="ot">[</span><span class="st">'name'</span><span class="ot">],</span>
<span class="st">'age'</span> => <span class="kw">$val</span><span class="ot">[</span><span class="st">'age'</span><span class="ot">],</span>
<span class="ot">];</span>
}
<span class="kw">$list</span><span class="ot">[</span><span class="st">'count'</span><span class="ot">]</span> = <span class="fu">count</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">);</span> <span class="co">// 其他属性</span>
<span class="fu">echo</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$list</span><span class="ot">);</span> <span class="co">// 输出 json</span>
<span class="co">// {"1":{"name":"zhangsan","age":22},"2":{"name":"lisi","age":25},"count":2}</span></code>而最后一种是比较常用的写法，自定义字段和数组一起用，来修改下刚才例子。
<code class="sourceCode php"><span class="kw">$arr</span> = <span class="kw">$User</span>->where<span class="ot">(</span><span class="kw">$where</span><span class="ot">)</span>->find<span class="ot">();</span> <span class="co">// 读取数据</span>
<span class="kw">$list</span> = <span class="ot">[];</span>
<span class="kw">foreach</span><span class="ot">(</span><span class="kw">$arr</span> <span class="kw">as</span> <span class="kw">$key</span> => <span class="kw">$val</span><span class="ot">)</span> { <span class="co">// 遍历数组</span>
<span class="kw">$list</span><span class="ot">[</span><span class="st">'list'</span><span class="ot">][]</span> = <span class="ot">[</span> <span class="co">// 修改这里</span>
<span class="st">'name'</span> => <span class="kw">$val</span><span class="ot">[</span><span class="st">'name'</span><span class="ot">],</span>
<span class="st">'age'</span> => <span class="kw">$val</span><span class="ot">[</span><span class="st">'age'</span><span class="ot">],</span>
<span class="ot">];</span>
}
<span class="kw">$list</span><span class="ot">[</span><span class="st">'count'</span><span class="ot">]</span> = <span class="fu">count</span><span class="ot">(</span><span class="kw">$arr</span><span class="ot">);</span> <span class="co">// 其他属性</span>
<span class="fu">echo</span> <span class="fu">json_encode</span><span class="ot">(</span><span class="kw">$list</span><span class="ot">);</span> <span class="co">// 输出 json</span>
<span class="co">// {"list":[{"name":"zhangsan","age":22},{"name":"lisi","age":25}],"count":2}</span></code>OK，希望对刚入门的 phper 有所帮助。
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