PHP's json format and js cross-domain calling code

function jsontest()
{
var json = [{'username':'crystal','userage':'20'},{'username':'candy','userage ':'24'}];
alert(json[1].username);
var json2 = [['crystal','20'],['candy','24 ']];
alert(json2[0][0]);
}

This function, the first alert(json[1].username); will prompt "candy". The json variable is an array object. So it needs to be called in the format of obj.username. The second alert(json2[0][0]); will prompt "crystal". The json2 variable is a complete json format. Both json and json2 variables achieve the same effect, but json2 is obviously much more streamlined than json. This is JavaScript's json format. Let's take a look at the json format in php. Let's look at a piece of code first:

$arr = array (
array (
'catid' => '4',
'catname' => 'Rongrong',
'meta_title' => ' Rongrong Blog'
),
array (
'catid' => '6',
'catname' => 'climber',
'meta_title' => 'Climbing or',
)
);
$jsonstr = json_encode($arr);
echo $jsonstr;

In this code, $arr is an array, we use json_encode converts $arr to json format. This code will output: [{"catid":"4","catname":"u7a0bu7a0b","meta_title":"u7a0bu7a0bu535au5ba2"},{"catid":"6","catname":"climber","meta_title":"u6500u767bu8005 "}] This is how php handles json data. For json data, PHP can also use the json_decode() function to convert json data into an array. For example, in the above code, we use the json_decode function to process it. The above array will be printed out again.

$jsonstr = json_encode($arr);
$jsonstr = json_decode($jsonstr);
print_r($jsonstr);

Next, take a look at php json data and js How json data calls each other.

Create a new file php_json.php:

$arr = array (
array (
'catid' => '4',
'catname' => 'Rongrong',
'meta_title ' => 'Rongrong Blog'
),
array (
'catid' => '6',
'catname' => 'climber',
'meta_title' => 'Climber',
)
);
$jsonstr = json_encode($arr);
-----The following is written outside the php range-----
var jsonstr=< ? = $ jsonstr ?>;

Note: At the end of the php_json.php file, there is the sentence var jsonstr=;. This is to assign json format data to the jsonstr variable. Create another file json.html:

In this way, when viewing json.html, loadjson(jsonstr) will prompt "Rongrong ” and “climber”. This also implements js cross-domain calling.