HOWTO · PHP
Constructor in PHP
This article shows how the PHP constructor can initialize the properties of an object created in a class.
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In this tutorial, we will introduce the PHP constructor. We will see how you can use the __construct() function to initialize the properties of an instance in a class.
We will also use the function to initialize the properties of objects with given parameters in a class.
Last, we will see how you can initiate an object in a child class and call the parent class constructor when both classes have individual constructors.
Use the PHP Constructor to Initialize the Properties of an Object in a Class
In the example below, we will create a class Student and use the __construct function to assign new Student its properties.
The __construct function reduces the number of codes associated with using the function set_name().
<?php
class Student {
// Define the attributes of your class
public $name;
public $email;
// Initialize the properties of the object you want to create in this class
function __construct($name, $email) {
$this->name = $name;
$this->email = $email;
}
function get_name() {
return $this->name;
}
function get_email() {
return $this->email;
}
}
$obj = new Student("John", "john567@gmail.com");
echo $obj->get_name();
echo "<br>";
echo $obj->get_email();
?>
Output:
John
john567@gmail.com
Use the PHP Constructor to Initialize the Properties of an Object with Parameters in a Class
In the example code below, we create the class Military and use the __construct function to give the properties and parameters of the objects we create.
<?php
class Military {
// Define the attributes of the class 'Military'
public $name;
public $rank;
function __construct($name, $rank){
$this->name = $name;
$this->rank = $rank;
}
function show_detail() {
echo $this->name." : ";
echo "Your Rank is ".$this->rank."\n";
}
}
$person_obj = new Military("Michael", "General");
$person_obj->show_detail();
echo "<br>";
$person2 = new Military("Fred", "Commander");
$person2->show_detail();
?>
Output:
Michael : Your Rank is General
Fred : Your Rank is Commander
Initiate an Object in a Child Class and Call the Parent Class Constructor When Both Classes Have Individual Constructors in PHP
<?php
class Student
{
public $name;
public function __construct($name)
{
$this->name = $name;
}
}class Identity extends Student
{
public $identity_id;
public function __construct($name, $identity_id)
{
parent::__construct($name);
$this->identity_id = $identity_id;
}
function show_detail() {
echo $this->name." : ";
echo "Your Id Number is ".$this->identity_id."\n";
}
}
$obj = new Identity('Alice', '1036398');
echo $obj->show_detail();
?>
Output:
Alice : Your Id Number is 1036398
The class Identity extends the class Student in the code above. We use the keyword parent: to call the constructor for the Student class.
