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 about the different phases of reading data from the database. We’ll learn how to prepare queries, bind parameters, define bound values, and execute queries.


# Step 1: Write a query

Write a regular select statement and instead of values, put named placeholders. For example:

```
$sql = "SELECT * FROM users WHERE city = :city";
```

# Step 2: Prepare the query to execute

Prepare the query:

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

Bind the parameters:

```
$query -> bindParam(':city', $city, PDO::PARAM_STR);
```

Define the bound value:

```
$city = "New York";
```

And execute the query:

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

# Step 3: Assign the data to a variable

Assign the data that we pulled from the database in the preceding step to a variable:

```
$results = $query -> fetchAll(PDO::FETCH_OBJ);
```

Here, we use the parameter `PDO::FETCH_OBJ` that returns the fetched data as an object. If we want to fetch the data in the form of an array, we can use `PDO::FETCH_ASSOC`.

# Step 4: Retrieve and display the data

Make sure that we’re able to retrieve the data from the database by counting the number of records:

```
if($query -> rowCount() > 0){}
```

In case the query returns at least one record, we can echo the records within a `foreach` loop:

```
if($query -> rowCount() > 0) {
   foreach($results as $result) {
      echo $result -> name . ", "; 
      echo $result -> city . ", "; 
      echo $result -> date_added;
   } 
}
```

Let’s do all the steps together now.

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

# Step 1: Write a query

Write a regular select statement and instead of values, put named placeholders. For example:

```
$sql = "SELECT * FROM users WHERE city = :city";
```

# Step 2: Prepare the query to execute

Prepare the query:

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

Bind the parameters:

```
$query -> bindParam(':city', $city, PDO::PARAM_STR);
```

Define the bound value:

```
$city = "New York";
```

And execute the query:

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

# Step 3: Assign the data to a variable

Assign the data that we pulled from the database in the preceding step to a variable:

```
$results = $query -> fetchAll(PDO::FETCH_OBJ);
```

Here, we use the parameter `PDO::FETCH_OBJ` that returns the fetched data as an object. If we want to fetch the data in the form of an array, we can use `PDO::FETCH_ASSOC`.

# Step 4: Retrieve and display the data

Make sure that we’re able to retrieve the data from the database by counting the number of records:

```
if($query -> rowCount() > 0){}
```

In case the query returns at least one record, we can echo the records within a `foreach` loop:

```
if($query -> rowCount() > 0) {
   foreach($results as $result) {
      echo $result -> name . ", "; 
      echo $result -> city . ", "; 
      echo $result -> date_added;
   } 
}
```

Let’s do all the steps together now.

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

Learn how to read data from 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

Reading Data from the Database

Step 1: Write a query

Step 2: Prepare the query to execute