The XML language is a way to structure data for sharing across websites.
Several web technologies like RSS Feeds and Podcasts are written in XML.
XML is easy to create. It looks a lot like HTML, except that you make up your own tags.
To read and update, create and manipulate an XML document, you will need an XML parser.
In PHP there are two major types of XML parsers:
MySQL provides a LIMIT clause that is used to specify the number of records to return.
The LIMIT clause makes it easy to code multi page results or pagination with SQL, and is very useful on large tables. Returning a large number of records can impact on performance. Continue reading PHP MySQL Limit Data Selections
The UPDATE statement is used to update existing records in a table:
UPDATE table_name
SET column1=value, column2=value2,...
WHERE some_column=some_value
Notice the WHERE clause in the UPDATE syntax: The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!
The DELETE statement is used to delete records from a table:
DELETE FROM table_name
WHERE some_column = some_value
Notice the WHERE clause in the DELETE syntax: The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!
The ORDER BY clause is used to sort the result-set in ascending or descending order.
The ORDER BY clause sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword.
SELECT column_name(s) FROM table_name ORDER BY column_name(s) ASC|DESC
The WHERE clause is used to filter records.
The WHERE clause is used to extract only those records that fulfill a specified condition.
SELECT column_name(s) FROM table_name WHERE column_name operator value
The SELECT statement is used to select data from one or more tables:
SELECT column_name(s) FROM table_name
or we can use the * character to select ALL columns from a table:
SELECT * FROM table_name
The following example selects the id, firstname and lastname columns from the MyGuests table and displays it on the page :
<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>
Code lines to explain from the example above :
First, we set up an SQL query that selects the id, firstname and lastname columns from the MyGuests table. The next line of code runs the query and puts the resulting data into a variable called $result. Continue reading PHP MySQL Select Data
Prepared statements are very useful against SQL injections.
A prepared statement is a feature used to execute the same (or similar) SQL statements repeatedly with high efficiency. Continue reading PHP MySQL Prepared Statements
Multiple SQL statements must be executed with the mysqli_multi_query() function.
The following examples add three new records to the “MyGuests” table : Continue reading PHP MySQL Insert Multiple Records
If we perform an INSERT or UPDATE on a table with an AUTO_INCREMENT field, we can get the ID of the last inserted/updated record immediately.
In the table “MyGuests”, the “id” column is an AUTO_INCREMENT field:
CREATE TABLE MyGuests (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
email VARCHAR(50),
reg_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
)
The following examples are equal to the examples from the previous page (PHP Insert Data Into MySQL), except that we have added one single line of code to retrieve the ID of the last inserted record. We also echo the last inserted ID: Continue reading PHP MySQL Get Last Inserted ID