PHP constructor with a parameter

Question

I need a function that will do something like this:

$arr = array(); // This is the array where I'm storing data

$f = new MyRecord(); // I have __constructor in class Field() that sets some default values
$f->{'fid'} = 1;
$f->{'fvalue-string'} = $_POST['data'];
$arr[] = $f;

$f = new Field();
$f->{'fid'} = 2;
$f->{'fvalue-int'} = $_POST['data2'];
$arr[] = $f;

When I write something like this:

$f = new Field(1, 'fvalue-string', $_POST['data-string'], $arr);
$f = new Field(2, 'fvalue-int', $_POST['data-integer'], $arr);

// Description of parameters that I want to use:
// 1 - always integer, unique (fid property of MyRecord class)
// 'fvalue-int' - name of field/property in MyRecord class where the next parameter will go
// 3. Data for field specified in the previous parameter
// 4. Array where the class should go

I don’t know how to make a parametrized constructor in PHP.

Now I use a constructor like this:

class MyRecord
{
    function __construct() {
        $default = new stdClass();
        $default->{'fvalue-string'} = '';
        $default->{'fvalue-int'} = 0;
        $default->{'fvalue-float'} = 0;
        $default->{'fvalue-image'} = ' ';
        $default->{'fvalue-datetime'} = 0;
        $default->{'fvalue-boolean'} = false;

        $this = $default;
    }
}

Peter Mortensen · Accepted Answer · 2019-11-20 01:08:53Z

157

Read all of Constructors and Destructors.

Constructors can take parameters like any other function or method in PHP:

class MyClass {

  public $param;

  public function __construct($param) {
    $this->param = $param;
  }
}

$myClass = new MyClass('foobar');
echo $myClass->param; // foobar

Your example of how you use constructors now won't even compile as you can't reassign $this.

Also, you don't need the curly brackets every time you access or set a property. $object->property works just fine. You only need to use curly-brackets under special circumstances like if you need to evaluate a method $object->{$foo->bar()} = 'test';

edited Nov 20, 2019 at 1:08

Peter Mortensen

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answered Feb 19, 2012 at 5:02

Mike B

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3 Comments

Kamil Over a year ago

You are right. It doesnt work. How i can initialize property {'fvalue-string'} with default value?

Kamil Over a year ago

I tried constructor with multiple parameters yesterday and they didnt worked, i was doing something wrong, because i got errors. I saw many examples of __construct(array) and "unpacking" array inside constructor, so i thought that i cant make constructor with many parameters in PHP. I was wrong. Thank you.

user1986815 Over a year ago

why do you make $param public ? ccan't you put return $param in the constructor and call the class like echo new MyClass('foobar') ?

Michael Robinson · Accepted Answer · 2012-02-19 05:06:13Z

30

If you want to pass an array as a parameter and 'auto' populate your properties:

class MyRecord {
    function __construct($parameters = array()) {
        foreach($parameters as $key => $value) {
            $this->$key = $value;
        }
    }
}

Notice that a constructor is used to create & initialize an object, therefore one may use $this to use / modify the object you're constructing.

answered Feb 19, 2012 at 5:06

Michael Robinson

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