When a user navigates in her browser to a page that ends with a .php extension, the request is sent to a web server, which directs the request to the PHP interpreter.


As shown in the diagram above, the PHP interpreter processes the page, communicating with file systems, databases, and email servers as necessary, and then delivers a web page to the web server to return to the browser.

The syntax of function is very similar to Javascript:

 function abc() {
     echo "I love PHP";
 }

 echo "Hello, World 
";
 abc();
?>

The output is:

Hello, World
I love PHP

You can put any PHP code into the function block. But you should keep in mind, to use a function, you must call functin name with "()". In the above the sample, we call the function:

abc();

We can pass parameters to a function:

function abc($count, $msg = "I love PHP") {
for($i = 0; $i < $count; $i++){
echo $msg . "
";
}
}

abc(5);

The output is that the value of $msg "I love PHP" will be displayed for 5 times.

We can use the return statements to assign a variable's value based on the results of the execution of a particular function. For example:

 function compareNum($v1, $v2) {
  if($v1 > $v2) {
   return "Yes";
  } else {
   return "No";
  }
 ?>

 $anwser = compareNum(8, 10);
 echo "Is 8 greater than 10? -- $answer!";
?>

The output will be:

Is 8 greater than 10? -- No!