How do I get an object's unqualified (short) class name?

You can do this with reflection. Specifically, you can use the ReflectionClass::getShortName method, which gets the name of the class without its namespace.

First, you need to build a ReflectionClass instance, and then call the getShortName method of that instance:

$reflect = new ReflectionClass($object);
if ($reflect->getShortName() === 'Name') {
    // do this
}

However, I can't imagine many circumstances where this would be desirable. If you want to require that the object is a member of a certain class, the way to test it is with instanceof. If you want a more flexible way to signal certain constraints, the way to do that is to write an interface and require that the code implement that interface. Again, the correct way to do this is with instanceof. (You can do it with ReflectionClass, but it would have much worse performance.)

(new \ReflectionClass($obj))->getShortName(); is the best solution with regards to performance.

I was curious which of the provided solutions is the fastest, so I've put together a little test.

Results

Reflection: 1.967512512207 s ClassA
Basename:   2.6840535163879 s ClassA
Explode:    2.6507515668869 s ClassA

Code

namespace foo\bar\baz;

class ClassA{
    public function getClassExplode(){
        return explode('\\', static::class)[0];
    }

    public function getClassReflection(){
        return (new \ReflectionClass($this))->getShortName();
    }

    public function getClassBasename(){
        return basename(str_replace('\\', '/', static::class));
    }
}

$a = new ClassA();
$num = 100000;

$rounds = 10;
$res = array(
    "Reflection" => array(),
    "Basename" => array(),
    "Explode" => array(),
);

for($r = 0; $r < $rounds; $r++){

    $start = microtime(true);
    for($i = 0; $i < $num; $i++){
        $a->getClassReflection();
    }
    $end = microtime(true);
    $res["Reflection"][] = ($end-$start);

    $start = microtime(true);
    for($i = 0; $i < $num; $i++){
        $a->getClassBasename();
    }
    $end = microtime(true);
    $res["Basename"][] = ($end-$start);

    $start = microtime(true);
    for($i = 0; $i < $num; $i++){
        $a->getClassExplode();
    }
    $end = microtime(true);
    $res["Explode"][] = ($end-$start);
}

echo "Reflection: ".array_sum($res["Reflection"])/count($res["Reflection"])." s ".$a->getClassReflection()."\n";
echo "Basename: ".array_sum($res["Basename"])/count($res["Basename"])." s ".$a->getClassBasename()."\n";
echo "Explode: ".array_sum($res["Explode"])/count($res["Explode"])." s ".$a->getClassExplode()."\n";

The results actually surprised me. I thought the explode solution would be the fastest way to go...

I added substr to the test of https://stackoverflow.com/a/25472778/2386943 and that's the fastet way I could test (CentOS PHP 5.3.3, Ubuntu PHP 5.5.9) both with an i5.

$classNameWithNamespace=get_class($this);
return substr($classNameWithNamespace, strrpos($classNameWithNamespace, '\\')+1);

Results

Reflection: 0.068084406852722 s ClassA
Basename: 0.12301609516144 s ClassA
Explode: 0.14073524475098 s ClassA
Substring: 0.059865570068359 s ClassA 

Code

namespace foo\bar\baz;
class ClassA{
  public function getClassExplode(){
    $c = array_pop(explode('\\', get_class($this)));
    return $c;
  }

  public function getClassReflection(){
    $c = (new \ReflectionClass($this))->getShortName();
    return $c;
  }

  public function getClassBasename(){
    $c = basename(str_replace('\\', '/', get_class($this)));
    return $c;
  }

  public function getClassSubstring(){
    $classNameWithNamespace = get_class($this);
    return substr($classNameWithNamespace, strrpos($classNameWithNamespace, '\\')+1);
  }
}

$a = new ClassA();
$num = 100000;

$rounds = 10;
$res = array(
    "Reflection" => array(),
    "Basename" => array(),
    "Explode" => array(),
    "Substring" => array()
);

for($r = 0; $r < $rounds; $r++){

  $start = microtime(true);
  for($i = 0; $i < $num; $i++){
    $a->getClassReflection();
  }
  $end = microtime(true);
  $res["Reflection"][] = ($end-$start);

  $start = microtime(true);
  for($i = 0; $i < $num; $i++){
    $a->getClassBasename();
  }
  $end = microtime(true);
  $res["Basename"][] = ($end-$start);

  $start = microtime(true);
  for($i = 0; $i < $num; $i++){
    $a->getClassExplode();
  }
  $end = microtime(true);
  $res["Explode"][] = ($end-$start);

  $start = microtime(true);
  for($i = 0; $i < $num; $i++){
    $a->getClassSubstring();
  }
  $end = microtime(true);
  $res["Substring"][] = ($end-$start);
}

echo "Reflection: ".array_sum($res["Reflection"])/count($res["Reflection"])." s ".$a->getClassReflection()."\n";
echo "Basename: ".array_sum($res["Basename"])/count($res["Basename"])." s ".$a->getClassBasename()."\n";
echo "Explode: ".array_sum($res["Explode"])/count($res["Explode"])." s ".$a->getClassExplode()."\n";
echo "Substring: ".array_sum($res["Substring"])/count($res["Substring"])." s ".$a->getClassSubstring()."\n";

==UPDATE==

As mentioned in the comments by @MrBandersnatch there is even a faster way to do this:

return substr(strrchr(get_class($this), '\\'), 1);

Here are the updated test results with "SubstringStrChr" (saves up to about 0.001 s):

Reflection: 0.073065280914307 s ClassA
Basename: 0.12585079669952 s ClassA
Explode: 0.14593172073364 s ClassA
Substring: 0.060415267944336 s ClassA
SubstringStrChr: 0.059880912303925 s ClassA