[PHP] json_decode 會失效的情況

一、Bug #42186 json_decode() won't work with \l
二、Tabs in Javascript strings break json_decode()
三、json_decode returns false when leading zeros aren't escaped with double quotes
四、decode chokes on unquoted object keys
一、Bug #42186 json_decode() won't work with \l

当字符串中含有 \l 的时候，json_decode是无法解析，测试代码：

echo "***********json_decode() won't work with \l************* ";
$json = '{"stringwithbreak":"line with a \lbreak!"}';
var_dump($json);//stringwithbreak":"line with a \lbreak!
var_dump(json_decode($json, true));//null

解决办法：
主要是将\l进行替换，当然如果真的需要‘\l’，我们就必须不使用json_decode进行解析，可以当作当个字符进行提交。

var_dump(str_replace("\\l", "", $json));//stringwithbreak":"line with a break!
print_r(json_decode(str_replace("\\l", "", $json), true));//Array ( [stringwithbreak] => line with a break! )

二、Tabs in Javascript strings break json_decode()
当字符串中含有 tab 键时，json_decode()无法解析，例如代码3-1

echo "
***********Tabs in Javascript strings break json_decode()*************
";
var_dump(json_decode('{ "abc": 12, "foo": "bar bar" }'));

执行后的返回结果为null

解决办法：
1、当遇到含有tab键输入的字符串时，我们应该避免使用json将数据传到php，然后使用php作为解析。
2、同样可以使用如下3-2代码方式进行替换

$myStr = '{ "abc": 12, "foo": "bar bar" }';
$replaceStr = str_replace(" ", "\\t", $myStr);
var_dump($replaceStr);
var_dump(json_decode($replaceStr ));

三、json_decode returns false when leading zeros aren't escaped with double quotes
当json的value值为number类型，而且该number以0开头，例如代码4-1

echo "
***********json_decode returns false when leading zeros aren't escaped with double quotes*************
";
$noZeroNumber = '{
  "test" : 6
}';
$zeroNumber= '{
  "test" : 06
}';
var_dump(json_decode($noZeroNumber));//object(stdClass)[1]
  public 'test' => int 6
var_dump(json_decode($zeroNumber));//null

或许对于这种问题很少出现，但是一旦出现了，我们就很难去查找问题的原因。


四、decode chokes on unquoted object keys
当key值没有使用引号时，会无法解析，例如代码5-1

echo "
***********decode chokes on unquoted object keys*************
";
var_dump(json_decode('{"a":"tan","model":"sedan"}'));//object(stdClass)[1]
  public 'a' => string 'tan' (length=3)
  public 'model' => string 'sedan' (length=5)
var_dump(json_decode('{a:"tan","model":"sedan"}'));//null

[ ref ]
> CSDN json_decode在php中的一些无法解析的字符串