Home >Backend Development >PHP Tutorial >Is this good for three nights - JSON&PHP, _PHP tutorial
hi
I went to eat hot pot last night, yes, you guessed it right, I am in Chengdu
My seniors are treating me tonight, and my gay friends are treating me to hotpot tomorrow. I am supposed to be busy this week and have to be high three nights in a row (single graduate students are so easily satisfied). So I have no choice but to stop doing my job and write and write (I can’t write anymore...)
1. JSON
-----Introduction-----
Javascript Object Notation, a lightweight data exchange format
---
Basic Grammar: Four Basic Rules
Parallel data are separated by commas; mapping is represented by colon; collections (arrays) of parallel data are represented by []; mapped collections (objects) are represented by {}
For example: Beijing has an area of 16,800 square kilometers and a permanent population of 16 million; Shanghai has an area of 6,400 square kilometers and a permanent population of 18 million
expressed in JSON format is:
[
{"City":"Beijing","Area":16800,"Population":1600},
{"City":"Shanghai","Area":6400,"Population":1800}
]
---
Advantages: Simple format, easy to read, write and transmit; supports multiple languages
Disadvantages: The character set must be Unicode; the syntax is too strict
2. PHP&MySQL
-----php built-in mysql function (2)-----
----Four fetch functions_get the results
---
$query=mysqli_query($con, 'select * from test');
print_r(mysqli_fetch_row($query));
The first fetch, mysql_fetch_row(), only returns the data of the first row; Note that it actually reads one row at a time, row by row, so it can all be output like this:
$query=mysqli_query($con, 'select * from test');
while($row=mysqli_fetch_row($query)){
print_r($row);
}
Moreover, if the number of calls is greater than the number of rows, data exceeding the number of rows will not be output and null will be returned
Array ( [0] => 1 [1] => Tom ) Array ( [0] => 2 [1] => Tom ) Array ( [0] => 3 [ 1] => Tom ) Array ( [0] => 4 [1] => Tom ) Array ( [0] => 5 [1] => ???? ) Array ( [0] = > 6 [1] => Tom ) Array ( [0] => 7 [1] => ???? )
You can see that the returned result is an index array
---
mysql_fetch_array()
$arr=mysqli_fetch_array($query);
print_r($arr);
Usage is similar, result:
Array ( [0] => 1 [id] => 1 [1] => Tom [name] => Tom )
Compare database data
mysql> SELECT * FROM TEST;
---- ------
| id | name |
---- ------
| 1 | Tom |
| 2 | Tom |
| 3 | Tom |
| 4 | Tom |
| 5 | ???? |
| 6 | Tom |
| 7 | ???? |
---- ------
So, row takes a piece of data to generate an index array; array defaults to taking a piece of data to generate an index array and an associative array
To put it simply, array can use key names, which is quite convenient:
echo $arr['name'];
But array is a little slower
At the same time, array also has an optional second parameter, you can choose which array/arrays to output
$arr=mysqli_fetch_array($query,MYSQL_ASSOC);
print_r($arr);
echo $arr['name'];
Get
Array ( [id] => 1 [name] => Tom ) Tom
MYSQL_ASSOC, MYSQL_NUM, MYSQL_BOTH are just three parameters
---
mysql_fetch_assoc()
Basically the same thing as in the previous section, the output is the same
---
mysql_fetch_object()
Returns an object
$obj=mysqli_fetch_object($query);
echo $obj->name;
echo "
";
print_r($obj);
Results
Tom
stdClass Object
(
[id] => 1
[name] => Tom
)
Similar to the row command, you can also output line by line