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In PHP, we have a copy keyword which performs a shallow copy by default. We can implement the method to create our custom deep copy.
In PHP all objects are assigned by reference. The next two examples perform a shallow and a deep copy on objects. The Object object will have a reference to the Color object. It passes the instance of the Color object to its constructor. We increment the id, change the red part of the color object, and change the size to "big".
The size is different: "small" vs "big".
But the red part of the color object is same for both instances: Changing member values of the cloned object did not affect the original object. Changing members of the referenced object has affected the original object too.
In other words, both objects refer to the same color object in memory. To change this behaviour, we will do a deep copy next.
The original object has retained its previous 23 value. PHP exceptions Exceptions are designed to handle the occurrence of exceptions, special conditions that change the normal flow of program execution. Exceptions are raised or thrown and initiated. During the execution of our application, many things might go wrong.
A disk might get full and we cannot save our file. An Internet connection might go down and our application tries to connect to a site. All these might result in a crash of our application. To prevent happening this, we must cope with all possible errors that might occur. For this, we can use the exception handling.
Exceptions are available since PHP 5. Most PHP errors still use the old error reporting and not exceptions.
This leads to an error. The error is not an exception and is not caught by the catch keyword. This exception is later caught by the catch keyword.
To find out more info, we call the getMessage method on the exception object. The Exception is a base class for all exceptions. We can create our own exceptions derived from this base class.
This class derives from the Exception class through the extends keyword. We give the exception a message "Exceeded the maximum value allowed". In other words, each class can only have one constructor defined. There are two ways how we can handle this.
The second solution uses a factory pattern. We instantiate the class with 2 and 3 parameters. Their initial value is "not specified". So the idea is: the code inside the constructor is dynamic; it depends on the arguments passed to it. This is done by the above code line. The first takes 2 parameters, the second takes 3. Create objects folder.
Create category. Add the following code inside our category. Open objects folder. Create product. When you fill out the form and clicked the "Create" button. Changes in the database. This file will show the main page of our web app. Put the following code inside it. This button, when clicked, will let us go back to the records list. Replace the "contents will be here" comments in the previous section with the following code.
Put the following code before the "set page header" comment of section 6. Put the following code inside our "product. An HTML table will hold our data. Put the following code after the section 6. Inside the "while" loop of the previous section, there is a comment "read one, edit and delete button will be here", replace that with the following code.
Create a new file and name it "paging. This will be used for pagination. Open your product.
Add the following method in the class. Put the following code after the closing "table" tag of section 6.
List of records, page 1. List of records, page 2. Please take a break or drink some coffee first! Replace the previous section's "contents will be here" comments with the following code. The following code will retrieve data that will populate our HTML form.
This is important because this will let the user know what exactly the record he is updating. Now we can put the latest values to each form elements. This is to pre-select the option of the current record. Replace the previouse section's comments "categories select drop-down will be here" with the following code.
Once assigned, it will update the database with those values using the update method. Open our "product. The update record form should look like the following.
When you submit the form, a message will be shown. A record was changed in the database. Put the following code before the "set page headers" comments of the previous section.