$str = 'Hello World!';
$str2 = "Hello World!";

$str3 = $str2.' '.$str1;

echo strlen($str3);

echo $str3[5];


echo substr($str3, 5, 6);

echo strtoupper($str3);

$ar1  = array(5, 4, 6, 9, "ali");

$ar2 = array(3=>5, 4=>6, 'ali'=>'Ahmad');

foreach ($ar2 as $key =>$val)
  echo "$key : $val <br/>";

asort($ar1);

ksort($ar1);

array_kieys($ar1);

array_values($ar1);

array_combine($ar1, $ar2);

$i = 100;

if ($i < 10)
  echo "less than";
else
  echo "greater than";

for ($i=0; $i < 10; $i++) echo $i;

$i = 0;

while ($i < 10){
  echo $i;
  $i++;
}

int preg_match  ( string $pattern  , string $subject  [, array &$matches  [, int $flags  [, int $offset  ]]] )

int preg_match_all  ( string $pattern  , string $subject  , array &$matches  [, int $flags  [, int $offset  ]] )

mixed preg_replace  ( mixed $pattern  , mixed $replacement  , mixed $subject  [, int $limit  [, int &$count  ]] )

$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '$2 $1 $3';
echo preg_replace($pattern, $replacement, $string);

class Student
{
    public $id = '81232';
    public function getId()
    {
       return $this->id;
    }
    
    public function setId($new_id){
      $this->id = $new_id;
    } 
}

  $s = new Student;
  $s->setId('82346188');
  echo $s->getId();
  echo $s->id;

<FORM ACTION="action.php" METHOD=POST>
.
.
.
</FORM>

session_start();

$_SESSION