Alter/Modify global functions return value as per need without touching your code with just one variable

Example.php

<?php
namespace {
    // This allow us to configure the behavior of the "global mock"
    $mockSocketCreate = false;

    include_once './SomeClass.php';

    /*$dummy = new \My\Nice\Namezpace\SomeClass;
    var_dump($dummy->doSomething());*/

    var_dump(\My\Nice\Namezpace\SomeClass::doSomething());
}

namespace My\Nice\Namezpace {
    // And this here, does the trick: it will override the socket_create()
    // function in your code *just for the namespace* where you are defining it.
    // This relies on the code above calling the socket_create function without
    // the leading backslash, so we trick SomeClass into calling our own function
    // inside that namespace instead of the global socket_create function.
    function strpos() {
        global $mockSocketCreate;
        // var_dump($mockSocketCreate);exit;
        if (isset($mockSocketCreate) && $mockSocketCreate === true) {
            return false;
        } else {
            return call_user_func_array('\strpos', func_get_args());
        }
    }

}

SomeClass.php

<?php

namespace My\Nice\Namezpace;

class SomeClass
{
    public static function doSomething()
    {
        // Notice how the global function "socket_create" is called without
        // the leading backslash (relative instead of absolute call in a
        // namespaced environment). This will let us later mock the call
        // by taking advantage of the relative-to-the-namespace call.
        $socket = strpos('Full string', 'str');
        if ($socket === false) {
            throw new \Exception('Ooops!');
        }
        return true;
    }

    public function __construct(){}
}