Any script or program that runs on a server and connects to a database may be subject to SQL injections if it does not take the appropriate measures. Php and Aspx are just examples, but any other language/technology could face the same issue, including perl, C, C#, Java, Ruby, Python, Node.js (Javascript) and many more. Conversely, it's not because it's PHP that it will necessarily be subject to SQL injections.
There's a strong correlation between the "learning curve" and the frequency of SQL injection, because languages/technologies for easy learning curves (like php) tend to draw more inexperienced programmers which may in turn make more such errors, but it's definitely not an absolute link.
Also, using the same language (such as php), someone coding using a higher-level framework such as Symfony or Drupal which add abstractions layers between the SQL database and the programmer is probably less prone to SQL injections than someone who uses directly the low-level SQL query functions.
As explained by Anders, the visible extension (or lack thereof) is also not necessarily an indication of the actual language or technology.