Gain insights into object-oriented programming in PHP. Discover classes, objects, methods, inheritance, and more. Build dynamic server-side applications using OOP techniques and PHP database management.

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Object-oriented programming is perhaps the dominant development paradigm for leading languages including Java, C#, and Python. The rich class and inheritance framework wasn’t fully implemented in modern PHP until 2015, and best practices for object-oriented programming are still emerging.

This course is an introduction to object-oriented programming in PHP. You’ll start with the basics of the OOP paradigm and get familiar with classes, objects, methods, and properties. You’ll then chain methods and properties using the this keyword before working with access modifiers and magic methods. With these basics down, you’ll take a deep dive into object-oriented programming in PHP, including inheritance, abstraction, polymorphism, and namespaces. After exploring exception handling, you’ll use these object-oriented techniques to build, manage, and edit a PHP database.

By the end of this course, you’ll be prepared to build dynamic server-side applications using object-oriented programming in PHP.

Object-Oriented Programming in PHP

In this lesson, we’ll learn the different phases of inserting data into the database. We’ll see how to write queries, bind placeholders, assign values to variables, and finally execute them.


# Step 1: Write a query

Write a regular SQL query but, instead of values, put named placeholders. For example:

```
$sql = "INSERT INTO `users`
        (`name`, `phone`, `city`, 
        `date_added`)
        VALUES
        (:name,:phone,:city,:date)";
```

The use of placeholders is known as **prepared statements**. We use prepared statements as templates that we can later fill with actual values.


# Step 2: Prepare the query

```
$query = $dbh -> prepare($sql);
```

# Step 3: Bind placeholders to the variables

```
$query->bindParam(':name',$name);
```

We can add a third parameter that filters the data before it reaches the database:

```
$query->bindParam(':name',$name,PDO::PARAM_STR);
$query->bindParam(':phone',$phone,PDO::PARAM_INT);
$query->bindParam(':city',$city,PDO::PARAM_STR);
$query->bindParam(':date',$date,PDO::PARAM_STR);
```

* `PDO::PARAM_STR` is used for strings.
* `PDO::PARAM_INT` is used for integers.
* `PDO::PARAM_BOOL` allows only boolean (true/false) values. 
* `PDO::PARAM_NULL` allows only the NULL data type.

# Step 4: Assign values to the variables

```
$name  = "Joe";
$phone = "1231234567";
$city  = "New York";
$date  = date('Y-m-d');
```

# Step 5: Execute the query

```
$query -> execute();
```

Check that the insertion really worked using the following command:

```
$lastInsertId = $dbh->lastInsertId();
if($lastInsertId>0) {
   echo "OK"; 
}
else
{
   echo "not OK";
}
```

If the last inserted ID is greater than zero, the insertion worked.

Let’s do all the steps together now in the code widget below.

> **Note:** The database provided is not persistent and will _not_ save any data.

> **Note:** The `$dbh` variable contains the database connection, which has been already initialized for the code below. The hidden code is given below.


# Step 1: Write a query

Write a regular SQL query but, instead of values, put named placeholders. For example:

```
$sql = "INSERT INTO `users`
        (`name`, `phone`, `city`, 
        `date_added`)
        VALUES
        (:name,:phone,:city,:date)";
```

The use of placeholders is known as **prepared statements**. We use prepared statements as templates that we can later fill with actual values.


# Step 2: Prepare the query

```
$query = $dbh -> prepare($sql);
```

# Step 3: Bind placeholders to the variables

```
$query->bindParam(':name',$name);
```

We can add a third parameter that filters the data before it reaches the database:

```
$query->bindParam(':name',$name,PDO::PARAM_STR);
$query->bindParam(':phone',$phone,PDO::PARAM_INT);
$query->bindParam(':city',$city,PDO::PARAM_STR);
$query->bindParam(':date',$date,PDO::PARAM_STR);
```

* `PDO::PARAM_STR` is used for strings.
* `PDO::PARAM_INT` is used for integers.
* `PDO::PARAM_BOOL` allows only boolean (true/false) values. 
* `PDO::PARAM_NULL` allows only the NULL data type.

# Step 4: Assign values to the variables

```
$name  = "Joe";
$phone = "1231234567";
$city  = "New York";
$date  = date('Y-m-d');
```

# Step 5: Execute the query

```
$query -> execute();
```

Check that the insertion really worked using the following command:

```
$lastInsertId = $dbh->lastInsertId();
if($lastInsertId>0) {
   echo "OK"; 
}
else
{
   echo "not OK";
}
```

If the last inserted ID is greater than zero, the insertion worked.

Let’s do all the steps together now in the code widget below.

> **Note:** The database provided is not persistent and will _not_ save any data.

> **Note:** The `＄dbh` variable contains the database connection, which has been already initialized for the code below. The hidden code is given below.


Learn how to insert data into the database using PHP PDO.

Introduction

Classes and Objects

Using the $this Keyword for Chaining Methods and Properties

Access Modifiers

Magic Methods and Constants Unveiled

Inheritance in Object-oriented Programming

Abstract Classes and Interfaces

Polymorphism and Type Hinting

Static Methods & Properties and Traits

Namespaces & Dependency Injection

Exception Handling

PHP Database

Model-view-controller (MVC)

Conclusion

Appendix

Inserting Data into the Database

Step 1: Write a query

Step 2: Prepare the query