Parsing the PDO::fetch() method in PHP

It is often necessary to query data in the database in PHP. PDO is the more mainstream connection method now. PDO::fetch() is the main method of querying data in PDO. This article will take you through Let’s take a look at how to use the fetch() method.

First let’s take a look at the syntax of the fetch() method:

fetch ( int $fetch_style = ?   , int $cursor_orientation = PDO::FETCH_ORI_NEXT   , int $cursor_offset = 0)

• $fetch_style: controls how the next line is returned to the caller

• $ursor_orientation: For a scrollable cursor represented by a PDOStatement object, this value determines which row will be returned to the caller.

• $offset: For a $cursor_orientation parameter setting, if it is PDO::FETCH_ORI_REL, get the position of the row relative to the cursor before calling PDOStatement::fetch(); if it is PDO:: FETCH_ORI_ABS, specifies the absolute row number of the row you want to get in the result set.

• The value returned when this method succeeds depends on the extraction type. In all cases, failure returns false.
  

Code Example

1. Connect to the database

<?php
$servername="localhost";
$username="root";
$password="root123456";
$dbname="my_database";
$pdo=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
echo "连接成功"."<br>";
$pdo->setAttribute(PDO::ATTR_CASE,PDO::CASE_UPPER);
$sql="select * from fate";
$statement=$pdo->prepare($sql);
$statement->execute();

2. Several modes of $fetch_style

// PDO::FETCH_ASSOC
$result=$statement->fetch(PDO::FETCH_ASSOC);
print_r($result);
echo "<br>";
// PDO::FETCH_NUM
$result=$statement->fetch(PDO::FETCH_NUM);
print_r($result);
echo "<br>";
// PDO::FETCH_BOTH
$result=$statement->fetch(PDO::FETCH_BOTH);
print_r($result);
echo "<br>";
// PDO::LAZY
$result=$statement->fetch(PDO::FETCH_LAZY);
print_r($result);
echo "<br>";
// PDO::OBJ
$result=$statement->fetch(PDO::FETCH_OBJ);
print_r($result);

输出：连接成功
Array
([ID] => 1[NAME] => saber[AGE] => 100)
Array
([0] => 2[1] => acher[2] => 77)
Array
([ID] => 3[0] => 3[NAME] => luncher[1] => luncher [AGE] => 56[2] => 56)
PDORow Object
([queryString] => select * from fate[ID] => 4[NAME] => cooker[AGE] => 18)
stdClass Object
([ID] => 5[NAME] => 张三[AGE] => 66)

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