More on PHP

functions

function functionName() {
    // code to be executed;
}

Function names are NOT case-sensitive.

<!DOCTYPE html>
<html>
<body>
<?php
function writeMsg() {
    echo "Hello world!";
}
writeMsg();
?>
</body>
</html>

function arguments

<!DOCTYPE html>
<html>
<body>
<?php
function familyName($fname) {
    echo "$fname.<br>";
}

familyName("san");
familyName("dan");
?>

</body>
</html>

default arguments

<!DOCTYPE html>
<html>
<body>

<?php
function setHeight($minheight = 50) {
    echo "The height is : $minheight <br>";
}

setHeight(350);
setHeight();
setHeight(135);
setHeight(80);
?>

</body>
</html>

Returning Values

<!DOCTYPE html>
<html>
<body>

<?php
function sum($x, $y) {
    $z = $x + $y;
    return $z;
}

echo "5 + 10 = " . sum(5,10) . "<br>";
echo "7 + 13 = " . sum(7,13) . "<br>";
echo "2 + 4 = " . sum(2,4);
?>
</body>
</html>

Scope of variables

global - variable declared outside function has global scope
local - inside the function

Static keyword

function with static keyword store their previous state

<!DOCTYPE html>
<html>
<body>

<?php
function myTest()
{
  static $x = 0;
  $b=5;
  echo "x= ". $x ."<br>";
  echo "b= " . $b . "<br>";
  $x++;
}
myTest(); // 0 5
echo "<br>";
myTest(); // 1 5
echo "<br>";
myTest(); // 2 5
?>
</body>
</html>

Superglobals

Several predefined variables in PHP are superglobals, which means that they are always accessible, regardless of scope and you can access them from any function, class or file without having to do anything special. The PHP superglobal variables are:

$GLOBALS
$_SERVER
$_REQUEST
$_POST
$_GET
$_FILES
$_ENV
$_COOKIE
$_SESSION

`$GLOBALS`

$GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods).
PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

<!DOCTYPE html>
<html>
<body>
<?php 
$x = 75;
$y = 25; 
function addition() {
    $GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y'];
}
addition();
echo $z;
?>
</body>
</html>

In the example above, since z is a variable present within the $GLOBALS array, it is also accessible from outside the function.

`$_SERVER`

$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations.

<!DOCTYPE html>
<html>
<body>

<?php 
echo $_SERVER['PHP_SELF'];
echo "<br>";
echo $_SERVER['SERVER_NAME'];
echo "<br>";
echo $_SERVER['HTTP_HOST'];
echo "<br>";
echo $_SERVER['HTTP_REFERER'];
echo "<br>";
echo $_SERVER['HTTP_USER_AGENT'];
echo "<br>";
echo $_SERVER['SCRIPT_NAME'];
?>
</body>
</html>

`$_REQUEST`

PHP $_REQUEST is used to collect data after submitting an HTML form.
$_REQUEST, by default, contains the contents of $_GET, $_POST and $_COOKIE.

<!DOCTYPE html>
<html>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // collect value of input field
    $name = htmlspecialchars($_REQUEST['fname']); 
    if (empty($name)) {
        echo "Name is empty";
    } else {
        echo $name;
    }
}
?>

</body>
</html>

`$_POST`

PHP $_POST is widely used to collect form data after submitting an HTML form with method="post".
$_POST is also widely used to pass variables.

<!DOCTYPE html>
<html>
<body>

<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // collect value of input field
    $name = $_POST['fname']; 
    if (empty($name)) {
        echo "Name is empty";
    } else {
        echo $name;
    }
}
?>
</body>
</html>

Form Handling

using POST

<!DOCTYPE html>
<html>

  <body>
    <form action="welcome.php" method="post">
      Name: <input type="text" name="name" /><br />
      E-mail: <input type="text" name="email" /><br />
      <input type="submit" />
    </form>
  </body>
</html>

<html>
<body>
  Welcome <?php echo $_POST["name"]; ?><br>
  Your email address is: <?php echo $_POST["email"]; ?>
</body>
</html>

using GET

<!DOCTYPE html>
<html>
<head>
  <title>get</title>
</head>
<body>
  <form action="welcome_get.php" method="get">
    <label> Name:  </label>
    <input type="text" id="name" name="name" /><br>
    <label> E-mail: </label>
    <input type="text" if="email" name="email" /><br>
    <input type="submit" value="submit">
  </form>
</body>
</html>

<html>
<body>
  Welcome <?php echo $_GET["name"]; ?><br>
  Your email address is: <?php echo $_GET["email"]; ?>
</body>
</html>