How many interfaces can a class implement in PHP?

Question

I'm looking for an answer to question which is not difficult, but I can't find out how many interfaces can be implemented by one class.

Is this possible?

class Class1 implements Interface1, Interface2, Interface3, Interface4 {
   .....
}

For all the similar examples I found, I've seen that there can be only 2 interfaces implemented by one class. But there isn't any info about what I'm looking for.

As long as there are no conflicting method names in those interfaces, I belive there is no practical limit. — Jiří Brabec, Feb 11 '15 at 13:11

score 48 · Accepted Answer · answered Feb 11 '15 at 13:13

48

There is no limit on the number of interfaces that you can implement. By definition, you can only extend (inherit) one class.

I would, as a practical matter, limit the number of Interfaces you do implement, lest your class become overly bulky and thus hard to work with.

answered Feb 11 '15 at 13:13

Machavity

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so you are saying, that this way is possible? `class Class1 implements Interface1, Interface2, Interface3, Interface4{` – Arnas Pečelis Feb 11 '15 at 13:15
4

I see no problem in implementing multiple thousands of interfaces. It makes work easier. – hek2mgl Feb 11 '15 at 13:15
@ArnasPečelis Correct. And you can namespace your interfaces as well – Machavity Feb 11 '15 at 13:20
2

Actually there is one limit: `memory_limit` – Yousha Aleayoub Mar 05 '19 at 11:57
1

@YoushaAleayoub While technically correct (allocate too much and PHP crashes), that's less of a programmatical limit and more of a hard one – Machavity Mar 05 '19 at 13:08

score 15 · Answer 2 · answered Feb 11 '15 at 13:21

15

You can implement as many class you want, there is no limitation in that.

class Class1 implements Interface1, Interface2, Interface3, Interface4, Interface5, Interface6{
   .....
}

This means this is right Hope this helps you

answered Feb 11 '15 at 13:21

Utkarsh Dixit

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score 7 · Answer 3 · edited Feb 16 '23 at 20:24

I wrote a script that proves the answer that the amount is not limited:

<?php

$inters_string = '';

$interfaces_to_generate = 9999;

for($i=0; $i <= $interfaces_to_generate; $i++) {
  $cur_inter = 'inter'.$i;
  $inters[] = $cur_inter;
  $inters_string .= sprintf('interface %s {} ', $cur_inter);
}

eval($inters_string); // creates all the interfaces due the eval (executing a string as code)

eval(sprintf('class Bar implements %s {}', implode(',',$inters))); // generates the class that implements all that interfaces which were created before

$quxx = new Bar();

print_r(class_implements($quxx));

You can modify the counter var in the for loop to make that script generate even more interfaces to be implemented by the class "Bar".

It easily works with up to 9999 interfaces (and obviously more) as you can see from the output of the last code line (print_r) when executing that script.

The computer's memory seems to be the only limitation for the amount of interfaces for you get an memory exhausted error when the number is too high

score 7 · Answer 4 · answered Feb 11 '15 at 13:21

7

Yes, more than two interfaces can be implemented by a single class.
From the PHP manual:

Classes may implement more than one interface if desired by separating each interface with a comma.

answered Feb 11 '15 at 13:21

0x5C91

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score 1 · Answer 5 · answered Feb 11 '15 at 13:13

1

The number of interfaces a class can implement is not logically limited.

answered Feb 11 '15 at 13:13

hek2mgl

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How many interfaces can a class implement in PHP?

5 Answers5