call_instance_method_with_static_style.php

<?php

class Foo
{
    public $bar;

    function __construct()
    {
        $this->bar = 'bar';
    }

    public function echoFoo()
    {
        echo 'foo';
    }

    public function echoBar()
    {
        Bar::echoBar();
    }
}

class Bar
{
    public function echoBar()
    {
        echo $this->bar;
    }
}

$foo = new Foo();
$foo->echoFoo();
$foo->echoBar();
echo "\n";

From PHP 5.4, if the error level is E_STRICT, "Strict Standards" warning occurs.

fooPHP Strict Standards:  Non-static method Bar::echoBar() should not be called statically, assuming $this from incompatible context in ... on line 19

Strict Standards: Non-static method Bar::echoBar() should not be called statically, assuming $this from incompatible context in ... on line 19
bar