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)
Recommended: 《2021 Summary of PHP interview questions (collection)》《php video tutorial》
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php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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