我有一些类似的json数据，现在我想统计所有节点"b"，如果给它们一个数字，如何获得指定的节点。
[
{
"a":[
{
"b":"aaa" //in case this is the first node "b", definition number 1
},
{
"b":"bbb" //this is the second node "b", definition number 2
}
]
},
{
"a":[
{
"b":"ccc" //this is the third node "b", definition number 3
},
{
"b":"ddd" //this is the forth node "b", definition number 4
}
]
},
{
"c":"eee"
}，
]
现在在这个例子中，有4个节点"b"，如何计数？以及如何在php代码中获得第三个节点"b"？
$json=json_decode($txt);
foreach($json as $data){
if($data->a){
foreach($data->a as $row){
echo $row->b.'<br />';
//count($row->b);
}
}
}
要计数，您必须保留一个计数器，如下所示：
$counter = 0;
$json = json_decode($txt);
foreach ($json as $data) {
if ($data->a) {
foreach($data->a as $row){
$counter++;
if ($counter == 3) {
echo 'Third "b": ' . $row->b . '<br />';
}
}
}
}
echo 'Number of "b"s: ' . $counter . '<br />';
根据您的代码，您可以使用isset运算符：
$json=json_decode($txt);
$count = 0;
foreach($json as $data){
if($data->a){
foreach($data->a as $row){
if (isset($row->b))
++$count;
}
}
}
echo $count;
$json = json_decode($txt); echo count($json, COUNT_RECURSIVE);