If I want to execute a php script, i just point the browser to www.something.com/myscript.php
But if i want to execute a specific function inside
What your script does is entirely up to you. URLs cannot magically cause Apache, PHP, or any other server component to take a certain behavior, but if you write your program such that a particular function can be executed, it's certainly possible. Perhaps something like:
switch($_GET['function']) {
case 'specificFunction':
specificFunction();
}
Then you could visit myScript.php?function=specificFunction
Be extremely careful here to specifically list each allowable function. You must not just take the $_GET['function'] parameter and blindly execute whatever function it says, since that could present an enormous security risk.