PHP json format and js json format js cross domain call implementation code

So let's look at an js function

 
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); "candy" will be prompted. The json variable is an array object. So call it in a format like obj.username.
The second alert (json2 [0] [0]). "crystal" will be prompted. The json2 variable is fully in 1 json format. Both the json and json2 variables achieve the same effect, but json2 is significantly more streamlined than json.
This is json for JavaScript.
Let's take a look at the json format in php.
So let's look at one piece of code

 
$arr = array ( 
array ( 
'catid' => '4', 
'catname' => ' Love never fails ', 
'meta_title' => ' Love never fails blog ' 
), 

array ( 
'catid' => '6', 
'catname' => 'climber', 
'meta_title' => ' The climber ', 
) 
); 
$jsonstr = json_encode($arr); 
echo $jsonstr; 

In this code, $arr is an array. We use json_encode to convert $arr to json.
This code will output:

[{"catid":"4","catname":"\u7a0b\u7a0b","meta_title":"\u7a0b\u7a0b\u535a\u5ba2"},{"catid":"6","catname":"climber","meta_title":"\u6500\u767b\u8005"}]
This is what php does with json data.
For json data, php can also convert json data into an array using the json_decode() function.
For example, in the above code, we use the json_decode function. It will print out the array above.
$jsonstr = json_encode($arr);
$jsonstr = json_decode($jsonstr);
print_r($jsonstr);
Next, let's look at how php json data and js json data call each other.

We create a new php_json.php file

The code is as follows:

 
$arr = array ( 
array ( 
'catid' => '4', 
'catname' => ' Love never fails ', 
'meta_title' => ' Love never fails blog ' 
), 

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

PS: at the end of php_json.php file var jsonstr= < ? = $jsonstr ? > ; This one sentence. This is assigning data in json format to the jsonstr variable.
Let's create another json.html file

The code is as follows:

 
<SCRIPT type=text/javascript src="php_json.php"></SCRIPT><SCRIPT language=javascript type=text/javascript> 
function loadjson(_json) 
{ 
if(_json) 
{ 
for(var i=0;i<_json.length;i++) 
{ 
alert(_json[i].catname); 
} 
} 
} 

loadjson(jsonstr) 
</SCRIPT> 

This way, when we look at json.html, loadjson(jsonstr) will prompt "program" and "climber"
This also implements js cross-domain calls.