understanding php handling of static methods (non-static method cannot be called statically)

Question

<?php

class T {
        public function x(){
                return true;
        }    
}
var_dump(T::x());

class X {
        public function x(){
                return true;
        }

}    
var_dump(X::x());

This code results in:

bool(true)
PHP Fatal error:  Non-static method X::x() cannot be called statically in test.php on line 16

Why does T::x() works (when it should fail) and X::x() fails (as it should)?

well, self, parent and static are also doing non-static calls. Are you sure that $x = T::x(); is successful?! — bwoebi
– bwoebi, Commented Oct 10, 2013 at 17:47
Notice that in testY(), you are making a T object but not an X object. That seems to be making a difference. — Dillon Welch
– Dillon Welch, Commented Oct 10, 2013 at 17:57
@bwoebi that's exactly what i find strange in all this. I copy pasted the core i'm running. feel free to reproduce and see if it works any different. also, will update with my php/phpunit versions, that may be useful. — gcb
– gcb, Commented Oct 10, 2013 at 18:15
@gcb please modify your question a bit as it actually is totally unrelated to phpunit… (and it should be searchable by google with more obvious search queries…) 3v4l.org/l5v8p is much more comprehensive as a question… — bwoebi
– bwoebi, Commented Oct 10, 2013 at 18:30

gcb · Accepted Answer · 2015-01-08 23:17:21Z

3

X::x() is actually a PHP4 style constructor, as it share the same name of the class. And calling constructors of a class in a static way raises a fatal error:

Non-static method X::x() cannot be called statically, assuming $this from incompatible context

This actually is the case for all non-static magic methods as you can see in the implementation: http://lxr.php.net/xref/PHP_5_5/Zend/zend_compile.c#1636

The only case where it might be implicitely called statically (and raise an E_STRICT) is when the function has no special handling:

if (some large if/else's for the magic methods) {
    // flag isn't set…
} else {
    CG(active_op_array)->fn_flags |= ZEND_ACC_ALLOW_STATIC;
}

edited Jan 8, 2015 at 23:17

gcb

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answered Oct 10, 2013 at 18:24

bwoebi

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5 Comments

bwoebi Over a year ago

@gcb because T::x() isn't a PHP4 style constructor (and this way not a magic method what allows static calls from incompatible context)? For backwards compatibility, if PHP 5 cannot find a __construct() function for a given class, and the class did not inherit one from a parent class, it will search for the old-style constructor function, by the name of the class. from php.net/manual/en/language.oop5.decon.php

gcb Over a year ago

i still can't see how T::x() is any different than X::x(). If i remove the first test, which creates new T() from the code, the same thing happens. T::x() does not throw error. but X::() does.

bwoebi Over a year ago

@gcb X::x() is a constructor because the method name (x) is equal to the class name (X) (when ignoring case). T::x() is not a constructor because the method name (x) isn't equal to the class name (T). And as said in my answer: static calls on constructors fatal.

gcb Over a year ago

ah! of course! sorry, for some reason wasn't seeing that even with the previous explanations!

Dvid Silva Over a year ago

keep in mind that apparently is not case sensitive when calling classes, so x and X are the same

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