PHP MySQL Connect to a Database
The free MySQL database is very often used with PHP.
Create a Connection to a MySQL Database
Before you can access data in a database, you must create a connection to
the database.
In PHP, this is done with the mysql_connect() function.
Syntax
mysql_connect(servername,username,password);
|
Parameter
|
Description
|
|
servername
|
Optional. Specifies the server to connect to. Default
value is "localhost:3306"
|
|
username
|
Optional. Specifies the username to log in with. Default
value is the name of the user that owns the server process
|
|
password
|
Optional. Specifies the password to log in with. Default
is ""
|
Note: There are more available parameters, but the ones listed above
are the most important. Visit our full
PHP MySQL Reference
for more details.
Example
In the following example we store the connection in a variable ($con) for
later use in the script. The "die" part will be executed if the
connection fails:
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
// some code
?>
Closing a Connection
The connection will be closed automatically when the script ends. To close
the connection before, use the mysql_close() function:
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
// some code
mysql_close($con);
?>
PHP MySQL Create Database and Tables
A database holds one or multiple tables.
Create a Database
The CREATE DATABASE statement is used to create a database in MySQL.
Syntax
CREATE DATABASE database_name
To get PHP to execute the statement above we must use the mysql_query()
function. This function is used to send a query or command to a MySQL
connection.
Example
The following example creates a database called "my_db":
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
if (mysql_query("CREATE DATABASE my_db",$con))
{
echo "Database created";
}
else
{
echo "Error creating database: " . mysql_error();
}
mysql_close($con);
?>
Create a Table
The CREATE TABLE statement is used to create a table in MySQL.
Syntax
CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
column_name3 data_type,
....
)
We must add the CREATE TABLE statement to the mysql_query() function to
execute the command.
Example
The following example creates a table named "Persons", with three
columns. The column names will be "FirstName", "LastName"
and "Age":
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
// Create database
if (mysql_query("CREATE DATABASE my_db",$con))
{
echo "Database created";
}
else
{
echo "Error creating database: " . mysql_error();
}
// Create table
mysql_select_db("my_db", $con);
$sql = "CREATE TABLE Persons
(
FirstName varchar(15),
LastName varchar(15),
Age int
)";
// Execute query
mysql_query($sql,$con);
mysql_close($con);
?>
Important: A database must be selected before a table can be created.
The database is selected with the mysql_select_db() function.
Note: When you create a database field of type varchar, you must
specify the maximum length of the field, e.g. varchar(15).
The data type specifies what type of data the column can hold. For a
complete reference of all the data types available in MySQL, go to our complete
Data
Types reference.
Primary Keys and Auto Increment Fields
Each table should have a primary key field.
A primary key is used to uniquely identify the rows in a table. Each primary
key value must be unique within the table. Furthermore, the primary key field
cannot be null because the database engine requires a value to locate the
record.
The following example sets the personID field as the primary key field. The
primary key field is often an ID number, and is often used with the
AUTO_INCREMENT setting. AUTO_INCREMENT automatically increases the value of the
field by 1 each time a new record is added. To ensure that the primary key
field cannot be null, we must add the NOT NULL setting to the field.
Example
$sql = "CREATE TABLE Persons
(
personID int NOT NULL AUTO_INCREMENT,
PRIMARY KEY(personID),
FirstName varchar(15),
LastName varchar(15),
Age int
)";
mysql_query($sql,$con);
PHP MySQL Insert Into
The INSERT INTO statement is used to insert new records in a
table.
Insert Data Into a Database Table
The INSERT INTO statement is used to add new records to a database table.
Syntax
It is possible to write the INSERT INTO statement in two forms.
The first form doesn't specify the column names where the data will be
inserted, only their values:
INSERT INTO table_name
VALUES (value1, value2, value3,...)
The second form specifies both the column names and the values to be
inserted:
INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
To get PHP to execute the statements above we must use the mysql_query()
function. This function is used to send a query or command to a MySQL
connection.
Example
In the previous chapter we created a table named "Persons", with three
columns; "Firstname", "Lastname" and "Age". We
will use the same table in this example. The following example adds two new
records to the "Persons" table:
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("my_db", $con);
mysql_query("INSERT INTO Persons (FirstName, LastName, Age)
VALUES ('Peter', 'Griffin',35)");
mysql_query("INSERT INTO Persons (FirstName, LastName, Age)
VALUES ('Glenn', 'Quagmire',33)");
mysql_close($con);
?>
Insert Data From a Form Into a Database
Now we will create an HTML form that can be used to add new records to the
"Persons" table.
Here is the HTML form:
<html>
<body>
<form action="insert.php" method="post">
Firstname: <input type="text" name="firstname">
Lastname: <input type="text" name="lastname">
Age: <input type="text" name="age">
<input type="submit">
</form>
</body>
</html>
When a user clicks the submit button in the HTML form in the example above,
the form data is sent to "insert.php".
The "insert.php" file connects to a database, and retrieves the
values from the form with the PHP $_POST variables.
Then, the mysql_query() function executes the INSERT INTO statement, and a
new record will be added to the "Persons" table.
Here is the "insert.php" page:
<?php
$con =
mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("my_db", $con);
$sql="INSERT INTO Persons (FirstName, LastName, Age)
VALUES
('$_POST[firstname]','$_POST[lastname]','$_POST[age]')";
if (!mysql_query($sql,$con))
{
die('Error: ' . mysql_error());
}
echo "1 record added";
mysql_close($con);
?>
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