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This article introduces the relevant knowledge of "how to connect to the database with php pdo". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

To use php to connect to the database, you must first instantiate the pdo class, and have the data source, server account number, server password pdo connection database point is to achieve the conversion between different databases, and there is a transaction function of rollback, but also pdo::prepare (); pdo:::execute () function pre-processing query.

A data source is a collection of database types, server names, and database names.

Query ("set names gbk"); / / set the encoding format of the data passed from the database? >

Transaction introduction: I will explain the transaction introduction through my own understanding, that is, first turn off the automatic commit function of the database (what is the automatic commit function? That is, when we finish writing a sql statement, we can't afford to press enter, but we have to go through special code processing before submitting it, which I will introduce later.)

Then write the sql statement you want to execute and assign the returned results to two different variables, and then commit. If one or more of the errors occur during execution, the transaction rollback will be carried out. Even if you return to the initial state (that is, all the statements inserted or changed or deleted or queried in the transaction code are invalidated), another advantage is that you will not enter other web pages. Or execute other sql statements that affect the transaction

/ / the following is a brief introduction to the code for transaction rollback query ("set names gbk"); / / sets the encoding format of the data passed from the database $pdo- > begintransaction (); / / turns off the automatic commit function of mysql here $axithropdo-> query ("insert into tongxue values ('130042106 mother' Tan Yong', 'male'); $baked rollback Pdo-> query (" insert into tongxue values ('130042100' Zhu Bajie', 'male') "); if ($a==true & & $b==true) {$pdo- > commit () / / commit transaction} else {$pdo- > rollback (); / / transaction rollback}? >

The mysql_num_rows () function can count the rows of the result set returned by the database to determine whether the user name and password entered by the user are correct, so how do we achieve this function in pdo?

In pdo, there is a function pdo::fetchall (). Its function is to assign all the result sets returned from the database to get its value, and then use the count () function to count the number of trips. The specific case code is as follows

Query ("set names gbk"); / set the encoding format of the data passed from the database $sql= "select * from tongxue where id='130042106'"; $shuju=pdo- > prepare ($sql); / / this is what we call preprocessing $shuju- > execute (); / / the result of preprocessing; $jg=$shuju- > fetchall (PDO::FETCH_ASSOC); / / returns all the returned result sets to the variable $jg$hangshu=count ($jg) as an array. / / count the number of rows in the result set if ($hangshu > 0) {echo 'query shows that there is such person';} else {echo 'query shows that there is no such person';}? >

When our page runs a lot of sql statements, we can use the preprocessing in pdo to ease the pressure on the server, which is a good choice for projects that want to do large websites, because large websites get tens of thousands or hundreds of thousands of views a day.

Let's take a look at the preprocessing of pdo.

Query ("set names gbk"); / / set the encoding format of the data passed from the database $sql= "insert into tongxue values ('130042100' teacher', 'male')"; / / the sql statement we are going to execute $shuju=$pdo- > prepare ($sql); / / preprocessing $shuju- > execute (); / / the sql statement if ($shuju) {echo 'execution succeeded';} else {echo 'execution failed' That's all for "how to connect to a database with php pdo". Thank you for your reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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