Can PHP instantiate an object from the name of the class as a string?

Is it possible in PHP to instantiate an object from the name of a class, if the class name is stored in a string?

Yep, definitely.

$className = 'MyClass';
$object = new $className; 

if your class need arguments you should do this:

class Foo 
{
   public function __construct($bar)
   {
      echo $bar; 
   }
}

$name = 'Foo';
$args = 'bar';
$ref = new ReflectionClass($name);
$obj = $ref->newInstanceArgs(array($args));

Yes it is:

<?php

$type = 'cc';
$obj = new $type; // outputs "hi!"

class cc {
    function __construct() {
        echo 'hi!';
    }
}

?>

Static too:

$class = 'foo';
return $class::getId();

You can do some dynamic invocation by storing your classname(s) / methods in a storage such as a database. Assuming that the class is resilient for errors.

sample table my_table
    classNameCol |  methodNameCol | dynamic_sql
    class1 | method1 |  'select * tablex where .... '
    class1 | method2  |  'select * complex_query where .... '
    class2 | method1  |  empty use default implementation

etc.. Then in your code using the strings returned by the database for classes and methods names. you can even store sql queries for your classes, the level of automation if up to your imagination.

$myRecordSet  = $wpdb->get_results('select * from my my_table')

if ($myRecordSet) {
 foreach ($myRecordSet   as $currentRecord) {
   $obj =  new $currentRecord->classNameCol;
   $obj->sql_txt = $currentRecord->dynamic_sql;
   $obj->{currentRecord->methodNameCol}();
}
}

I use this method to create REST web services.