php – Behaviour of is_callable on '/'

My colleague and I have encountered some rather odd behavour. Our environments are Ubuntu 11.10, PHP 5.3.6-13ubuntu3.6 with Suhosin-Patch, and Windows 7 PHP 5.3.5.

On our machines, the following code runs as one would expect:

<?php
function t() { }
var_dump(is_callable('/'));

With the output:

bool(false)

On one of our servers, CentOS release 5.7 (Final), PHP 5.3.8, the same code produces:

bool(true)

Without the t() function, is_callable performs as expected. Note that is_function behaves the same as is_callable in these tests.

Does anyone have any idea what could be causing this?

Edit:

It seems to only happen when a function named t is present, anything else, like b, c etc, and the output is as expected.

Edit – testing with more characters:

<?php
function t() { }
foreach(str_split('/[email protected]#$%^&*()-_+=`~;:[]{}\|\'"?.>,<') as $character) {
    if (is_callable($character)) var_dump($character, is_callable($character));
}

Outputs the following on the server:

string(1) "/"
bool(true)
string(1) "t"
bool(true)
string(1) "T"
bool(true)
string(1) "_" // gettext
bool(true)
string(1) ":" // With the t() function undefined, this remains callable on the server
bool(true)

On our environments, the output is as expected:

string(1) "t"
bool(true)
string(1) "T"
bool(true)

Edit – more information on cbuckley’s comment:

<?php 
ini_set('display_errors', 1);
error_reporting(E_ALL);
function t() { }
$v = '/'; $v();

Produces output: Call to undefined function /()

$name = '/';
$actual = null;
if (is_callable($name, false, $actual) && $name === $actual) {
    // Method is actually callable
}

Tags: phpphp