Table of Contents
JSON Eval Trick in PHP
decode
encode
eval
json
php
and
start
supply
Version
PHP从5.2版本开始提供json_encode()和json_decode()函数，分别用于JSON的序例化和反序列化。不幸的是，现在仍然有许多主机运行着PHP5.2之前的版本，所以就不得不自己动手写JSON解析了。
JSON Encode
JSON的编码并没有什么难度，要点就两个：
- 对Object、Array中的元素进行递归遍历，注意要将关联数组转换成JSON中的Object Literal。
- 对字符串内容中引号、换行符等特殊字符进行转义，并将非ASCII字符转换成Unicode转义序列的形式。
下面是JSON编码方法的实现：
<span class="sd">/**</span>
<span class="sd"> * JSON Encode</span>
<span class="sd"> * @warn Any input string must be UTF-8 encoding</span>
<span class="sd"> * @param {Any} $data Any type object to serialize.</span>
<span class="sd"> * @return {String} serialized json string.</span>
<span class="sd"> */</span>
<span class="k">function</span> <span class="nf">json_stringify</span><span class="p">(</span><span class="nv">$data</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_null</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="k">return</span> <span class="s1">'null'</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_scalar</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="k">return</span> <span class="nx">json_stringify_scalar</span><span class="p">(</span><span class="nv">$data</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="k">empty</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="k">return</span> <span class="s1">'[]'</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_object</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="p">{</span>
<span class="nv">$data</span><span class="o">=</span><span class="nb">get_object_vars</span><span class="p">(</span><span class="nv">$data</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="k">empty</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="k">return</span> <span class="s1">'{}'</span><span class="p">;</span>
<span class="p">}</span>
<span class="nv">$keys</span><span class="o">=</span><span class="nb">array_keys</span><span class="p">(</span><span class="nv">$data</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">$keys</span><span class="o">===</span><span class="nb">array_keys</span><span class="p">(</span><span class="nv">$keys</span><span class="p">))</span> <span class="p">{</span>
<span class="nv">$data</span><span class="o">=</span><span class="nb">array_map</span><span class="p">(</span><span class="nx">__FUNCTION__</span><span class="p">,</span><span class="nv">$data</span><span class="p">);</span>
<span class="k">return</span> <span class="s1">'['</span><span class="o">.</span><span class="nb">join</span><span class="p">(</span><span class="s1">','</span><span class="p">,</span><span class="nv">$data</span><span class="p">)</span><span class="o">.</span><span class="s1">']'</span><span class="p">;</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span><span class="c1">//不是有序数字下标的数组即视为关联数组</span>
<span class="nv">$a</span><span class="o">=</span><span class="k">array</span><span class="p">();</span>
<span class="k">foreach</span> <span class="p">(</span><span class="nv">$data</span> <span class="k">as</span> <span class="nv">$k</span><span class="o">=></span><span class="nv">$v</span><span class="p">)</span> <span class="p">{</span>
<span class="nv">$a</span><span class="p">[]</span><span class="o">=</span><span class="nx">json_stringify_scalar</span><span class="p">(</span><span class="nb">strval</span><span class="p">(</span><span class="nv">$k</span><span class="p">))</span><span class="o">.</span><span class="s1">':'</span><span class="o">.</span><span class="nx">json_stringify</span><span class="p">(</span><span class="nv">$v</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">return</span> <span class="s1">'{'</span><span class="o">.</span><span class="nb">join</span><span class="p">(</span><span class="s1">','</span><span class="p">,</span><span class="nv">$a</span><span class="p">)</span><span class="o">.</span><span class="s1">'}'</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">function</span> <span class="nf">json_stringify_scalar</span><span class="p">(</span><span class="nv">$v</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_bool</span><span class="p">(</span><span class="nv">$v</span><span class="p">))</span> <span class="p">{</span>
<span class="nv">$v</span> <span class="o">=</span> <span class="nv">$v</span><span class="o">?</span><span class="s1">'true'</span><span class="o">:</span><span class="s1">'false'</span><span class="p">;</span>
<span class="p">}</span> <span class="k">else</span> <span class="k">if</span> <span class="p">(</span><span class="nb">is_string</span><span class="p">(</span><span class="nv">$v</span><span class="p">))</span> <span class="p">{</span>
<span class="nv">$v</span><span class="o">=</span><span class="nb">addcslashes</span><span class="p">(</span><span class="nv">$v</span><span class="p">,</span><span class="s2">"</span><span class="se">\t\n\r\"</span><span class="s2">\/</span><span class="se">\\</span><span class="s2">"</span><span class="p">);</span><span class="c1">//转义特殊字符</span>
<span class="c1">//将所有非ASCII字符转换成Unicode Escape格式</span>
<span class="nv">$v</span><span class="o">=</span><span class="s1">'"'</span><span class="o">.</span><span class="nb">preg_replace_callback</span><span class="p">(</span><span class="s1">'|[^\x00-\x7F]+|'</span><span class="p">,</span><span class="s1">'_unicode_escape'</span><span class="p">,</span><span class="nv">$v</span><span class="p">)</span><span class="o">.</span><span class="s1">'"'</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">return</span> <span class="p">(</span><span class="nx">string</span><span class="p">)</span><span class="nv">$v</span><span class="p">;</span>
<span class="p">}</span>
<span class="k">function</span> <span class="nf">_unicode_escape</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span> <span class="p">{</span>
<span class="c1">//Warning:字符串必须为UTF-8编码</span>
<span class="nv">$s</span><span class="o">=</span><span class="nb">str_split</span><span class="p">(</span><span class="nb">iconv</span><span class="p">(</span><span class="s1">'UTF-8'</span><span class="p">,</span><span class="s1">'UCS-2BE'</span><span class="p">,</span><span class="nv">$s</span><span class="p">[</span><span class="mi">0</span><span class="p">]),</span><span class="mi">2</span><span class="p">);</span>
<span class="k">foreach</span> <span class="p">(</span><span class="nv">$s</span> <span class="k">as</span> <span class="nv">$i</span><span class="o">=></span><span class="nv">$c</span><span class="p">)</span> <span class="p">{</span>
<span class="nv">$s</span><span class="p">[</span><span class="nv">$i</span><span class="p">]</span><span class="o">=</span><span class="nb">sprintf</span><span class="p">(</span><span class="s1">'\u%02x%02x'</span><span class="p">,</span><span class="nb">ord</span><span class="p">(</span><span class="nv">$c</span><span class="p">{</span><span class="mi">0</span><span class="p">}),</span><span class="nb">ord</span><span class="p">(</span><span class="nv">$c</span><span class="p">{</span><span class="mi">1</span><span class="p">}));</span>
<span class="p">}</span>
<span class="k">return</span> <span class="nb">join</span><span class="p">(</span><span class="s1">''</span><span class="p">,</span><span class="nv">$s</span><span class="p">);</span>
<span class="p">}</span>
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JSON Decode
而将JSON转换成PHP中的对象就没有那么简单了，自己写Parser进行词法分析、语法分析是很累人的。反观在JavaScript中实现JSON Parse就简单多了，因为JSON本身即是JavaScript语言的子集，直接使用eval方法，就能将JSON字符串转换成JS中的对象。
其实，看到JavaScript中的eval方法，实在不能不联想到PHP也有一个eval，它们的功能是类似的，都是将字符串当作代码运行。不同的是，JS中的eval执行JS代码，PHP的eval执行PHP代码。Trick就在这里：要让PHP能直接用eval方法解析JSON，只要将JSON代码转换成PHP格式的代码就行了！如对于下面的JSON：
<span class="p">{</span>
<span class="nt">"name"</span><span class="p">:</span><span class="s2">"CJ"</span><span class="p">,</span>
<span class="nt">"age"</span><span class="p">:</span><span class="mi">18</span><span class="p">,</span>
<span class="nt">"tags"</span><span class="p">:[</span><span class="s2">"PHP"</span><span class="p">,</span><span class="s2">"JavaScript"</span><span class="p">,</span><span class="s2">"Python"</span><span class="p">,</span><span class="s2">"Haskell"</span><span class="p">],</span>
<span class="nt">"life"</span><span class="p">:{</span>
<span class="nt">"summary"</span><span class="p">:</span><span class="s2">"Too complex!"</span>
<span class="p">}</span>
<span class="p">}</span>
Copy after login
只要将其转换成这样的PHP代码就能直接eval了：
<span class="p">(</span><span class="nx">object</span><span class="p">)</span><span class="k">array</span><span class="p">(</span>
<span class="s2">"name"</span><span class="o">=></span><span class="s2">"CJ"</span><span class="p">,</span>
<span class="s2">"age"</span><span class="o">=></span><span class="mi">18</span><span class="p">,</span>
<span class="s2">"tags"</span><span class="o">=></span><span class="k">array</span><span class="p">(</span><span class="s2">"PHP"</span><span class="p">,</span><span class="s2">"JavaScript"</span><span class="p">,</span><span class="s2">"Python"</span><span class="p">,</span><span class="s2">"Haskell"</span><span class="p">),</span>
<span class="s2">"life"</span><span class="o">=></span><span class="p">(</span><span class="nx">object</span><span class="p">)</span><span class="k">array</span><span class="p">(</span>
<span class="s2">"summary"</span><span class="o">=></span><span class="s2">"Too complex!"</span>
<span class="p">)</span>
<span class="p">)</span>
Copy after login
而将JSON转换成PHP代码则只需很少的步骤与注意点：
最终的实现代码出人意料的简单：
<span class="sd">/**</span>
<span class="sd"> * JSON Decode</span>
<span class="sd"> * @param {String} $s The string json data.</span>
<span class="sd"> * @param {Boolean} [$assoc=false] Return assoc array if $assoc is true.</span>
<span class="sd"> * @return decode result corresponding object.</span>
<span class="sd"> */</span>
<span class="k">function</span> <span class="nf">json_parse</span><span class="p">(</span><span class="nv">$s</span><span class="p">,</span><span class="nv">$assoc</span><span class="o">=</span><span class="k">false</span><span class="p">)</span> <span class="p">{</span>
<span class="k">static</span> <span class="nv">$strings</span><span class="p">,</span><span class="nv">$count</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_string</span><span class="p">(</span><span class="nv">$s</span><span class="p">))</span> <span class="p">{</span>
<span class="nv">$s</span><span class="o">=</span><span class="nx">trim</span><span class="p">(</span><span class="nv">$s</span><span class="p">);</span>
<span class="nv">$strings</span><span class="o">=</span><span class="k">array</span><span class="p">();</span>
<span class="c1">//匹配字符串结束引号应该确保前面只能有偶数个'\'</span>
<span class="c1">//如 "ab\"c"中 \" 不能被视为字符串结束引号</span>
<span class="nv">$s</span><span class="o">=</span><span class="nb">preg_replace_callback</span><span class="p">(</span><span class="s1">'/"([\s\S]*?(?<!\\\\)(?:\\\\\\\\)*)"/'</span><span class="p">,</span><span class="nx">__FUNCTION__</span><span class="p">,</span><span class="nv">$s</span><span class="p">);</span>
<span class="c1">//去除特殊字符后做简单的安全检测</span>
<span class="nv">$clean</span><span class="o">=</span><span class="nb">str_replace</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">'true'</span><span class="p">,</span><span class="s1">'false'</span><span class="p">,</span><span class="s1">'null'</span><span class="p">,</span><span class="s1">'{'</span><span class="p">,</span><span class="s1">'}'</span><span class="p">,</span><span class="s1">'['</span><span class="p">,</span><span class="s1">']'</span><span class="p">,</span><span class="s1">','</span><span class="p">,</span><span class="s1">':'</span><span class="p">,</span><span class="s1">'#'</span><span class="p">,</span><span class="s1">'.'</span><span class="p">),</span><span class="s1">''</span><span class="p">,</span><span class="nv">$s</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">$clean</span> <span class="o">&&</span> <span class="o">!</span><span class="nb">is_numeric</span><span class="p">(</span><span class="nv">$clean</span><span class="p">))</span> <span class="p">{</span><span class="c1">//可能是格式不正确的JSON、恶意代码</span>
<span class="k">return</span> <span class="k">NULL</span><span class="p">;</span>
<span class="p">}</span>
<span class="nv">$s</span><span class="o">=</span><span class="nb">str_replace</span><span class="p">(</span>
<span class="k">array</span><span class="p">(</span><span class="s1">'{'</span><span class="p">,</span><span class="s1">'['</span><span class="p">,</span><span class="s1">']'</span><span class="p">,</span><span class="s1">'}'</span><span class="p">,</span><span class="s1">':'</span><span class="p">,</span><span class="s1">'null'</span><span class="p">),</span>
<span class="c1">//通过'(object)'类型转换将关联数组转换成stdClass instance</span>
<span class="k">array</span><span class="p">((</span><span class="nv">$assoc</span><span class="o">?</span><span class="s1">''</span><span class="o">:</span><span class="s1">'(object)'</span><span class="p">)</span><span class="o">.</span><span class="s1">'array('</span><span class="p">,</span><span class="s1">'array('</span><span class="p">,</span><span class="s1">')'</span><span class="p">,</span><span class="s1">')'</span><span class="p">,</span><span class="s1">'=>'</span><span class="p">,</span><span class="s1">'NULL'</span><span class="p">)</span>
<span class="p">,</span><span class="nv">$s</span><span class="p">);</span>
<span class="nv">$s</span><span class="o">=</span><span class="nb">preg_replace_callback</span><span class="p">(</span><span class="s1">'/#\d+#/'</span><span class="p">,</span><span class="nx">__FUNCTION__</span><span class="p">,</span><span class="nv">$s</span><span class="p">);</span>
<span class="c1">//抑制错误,如{3##}能通过上面的安全检测但却无法转换成正确的PHP代码</span>
<span class="o">@</span><span class="nv">$data</span><span class="o">=</span><span class="k">eval</span><span class="p">(</span><span class="s2">"return </span><span class="si">$s</span><span class="s2">;"</span><span class="p">);</span>
<span class="nv">$strings</span><span class="o">=</span><span class="nv">$count</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="c1">//GC</span>
<span class="k">return</span> <span class="nv">$data</span><span class="p">;</span>
<span class="p">}</span> <span class="k">elseif</span> <span class="p">(</span><span class="nb">count</span><span class="p">(</span><span class="nv">$s</span><span class="p">)</span><span class="o">></span><span class="mi">1</span><span class="p">)</span> <span class="p">{</span><span class="c1">//存储字符串</span>
<span class="nv">$strings</span><span class="p">[]</span><span class="o">=</span><span class="nx">_unicode_unescape</span><span class="p">(</span><span class="nb">str_replace</span><span class="p">(</span><span class="k">array</span><span class="p">(</span><span class="s1">'$'</span><span class="p">,</span><span class="s1">'\\/'</span><span class="p">),</span><span class="k">array</span><span class="p">(</span><span class="s1">'\\$'</span><span class="p">,</span><span class="s1">'/'</span><span class="p">),</span><span class="nv">$s</span><span class="p">[</span><span class="mi">0</span><span class="p">]));</span>
<span class="k">return</span> <span class="s1">'#'</span><span class="o">.</span><span class="p">(</span><span class="nv">$count</span><span class="o">++</span><span class="p">)</span><span class="o">.</span><span class="s1">'#'</span><span class="p">;</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span><span class="c1">//读取存储的值</span>
<span class="nv">$index</span><span class="o">=</span><span class="nx">substr</span><span class="p">(</span><span class="nv">$s</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span><span class="mi">1</span><span class="p">,</span><span class="nb">strlen</span><span class="p">(</span><span class="nv">$s</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span><span class="o">-</span><span class="mi">2</span><span class="p">);</span>
<span class="k">return</span> <span class="nv">$strings</span><span class="p">[</span><span class="nv">$index</span><span class="p">];</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">function</span> <span class="nf">_unicode_unescape</span><span class="p">(</span><span class="nv">$data</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">is_string</span><span class="p">(</span><span class="nv">$data</span><span class="p">))</span> <span class="p">{</span>
<span class="c1">//匹配 Unicode escape时，需要注意匹配'\u'前面只能有偶数个'\'，如'\\u5409'不应被匹配</span>
<span class="k">return</span> <span class="nb">preg_replace_callback</span><span class="p">(</span>
<span class="s1">'/(?<!\\\\)((?:\\\\\\\\)*)\\\\u([a-f0-9]{2})([a-f0-9]{2})/i'</span><span class="p">,</span>
<span class="nx">__FUNCTION__</span><span class="p">,</span><span class="nv">$data</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">return</span> <span class="nv">$data</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="nb">iconv</span><span class="p">(</span><span class="s2">"UCS-2BE"</span><span class="p">,</span><span class="s2">"UTF-8"</span><span class="p">,</span><span class="nb">chr</span><span class="p">(</span><span class="nx">hexdec</span><span class="p">(</span><span class="nv">$data</span><span class="p">[</span><span class="mi">2</span><span class="p">]))</span><span class="o">.</span><span class="nb">chr</span><span class="p">(</span><span class="nx">hexdec</span><span class="p">(</span><span class="nv">$data</span><span class="p">[</span><span class="mi">3</span><span class="p">])));</span>
<span class="p">}</span>
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性能
和PHP 5.2之后的C实现的JSON方法相比，这里的实现自然要慢近百倍，根本不是一个数量级上的。 PEAR上有一个纯PHP实现的JSON库：Services_JSON。作为比较，我做了一个简单的性能对比测试，结果是，Services_JSON的encode方法比json_stringify方法慢三四倍，而Services_JSON的decode方法更是比json_parse方法慢十几倍。 对于json_stringify方法，应该是主要得益于使用iconv先将UTF-8字符串转换成UCS-2BE，再转换成Unicode转义序列的形式，自然要比Services_JSON自己实现UTF-8到Unicode转义序列的转换性能更高。而json_parse方法，虽然一般的递归下降Parser只需要扫描一次JSON字符串，而这里的实现会扫描多次字符串，但由于都是使用的PHP Native字符串方法，再加上eval这个非常规手段，最终性能上反而要高出好几倍。
原文地址：http://jex.im/programming/json-eval-trick-in-php.html
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PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian
Dec 24, 2024 pm 04:42 PM
PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals. This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivati
7 PHP Functions I Regret I Didn't Know Before
Nov 13, 2024 am 09:42 AM
If you are an experienced PHP developer, you might have the feeling that you’ve been there and done that already.You have developed a significant number of applications, debugged millions of lines of code, and tweaked a bunch of scripts to achieve op
How To Set Up Visual Studio Code (VS Code) for PHP Development
Dec 20, 2024 am 11:31 AM
Visual Studio Code, also known as VS Code, is a free source code editor — or integrated development environment (IDE) — available for all major operating systems. With a large collection of extensions for many programming languages, VS Code can be c
Explain JSON Web Tokens (JWT) and their use case in PHP APIs.
Apr 05, 2025 am 12:04 AM
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
PHP Program to Count Vowels in a String
Feb 07, 2025 pm 12:12 PM
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
How do you parse and process HTML/XML in PHP?
Feb 07, 2025 am 11:57 AM
This tutorial demonstrates how to efficiently process XML documents using PHP. XML (eXtensible Markup Language) is a versatile text-based markup language designed for both human readability and machine parsing. It's commonly used for data storage an
Explain late static binding in PHP (static::).
Apr 03, 2025 am 12:04 AM
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases?
Apr 03, 2025 am 12:03 AM
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
