php"><?php $value1 = 1111; $value2 = 2222; $value2 = &$value1; $value1 = 8888; echo $value2; // Outputs 8888 \nVariables in PHP start with a $ symbol. Variable names must begin with a letter or an underscore, can only contain letters, numbers, and underscores, cannot have spaces, and are case-sensitive.\nphp"><?php // Example of comments // Single line comment /* Multi-line comment */ // Variables $name = "John Doe"; $age = 30; $height = 175.5; $number = 100; $number1 = 101; // Variable operations $sum = $number + $number1; echo $sum; // Assignment $new_name = $name; echo "<br>"; echo $new_name; $name = "New John Doe"; echo "<br>"; echo $new_name; echo "<br>"; echo $name; echo "<br>"; // Reference assignment $new_name2 = &$name; echo "new_name2: ". $new_name2; echo "<br>"; $name = "Changed to Jane Doe"; echo "new_name2: ". $new_name2; echo "<br>"; $new_name2 = "Hello"; echo "name: ". $name; // Variable variables $name = "abc"; $abc = "def"; $def = "123456789"; $test = $$name; echo $test; echo "<br>"; // var_dump for more information $bool = false; echo $bool; echo "<br>"; var_dump($bool); echo "<br>"; // isset checks if a variable is set $names = "123"; var_dump(isset($names)); var_dump(isset($names1)); $is_exists = isset($names); if ($is_exists) { echo "Variable exists"; } else { echo "Variable does not exist"; } // unset to delete a variable unset($names); var_dump(isset($names)); // Global variables var_dump($_SERVER); var_dump($_COOKIE); var_dump($_SESSION); var_dump($_GET); var_dump($_POST); var_dump($_REQUEST); // Constants define('CONST_NAME', 'Value'); echo CONST_NAME; // Data types $int_val = 100; var_dump($int_val); $float_val = 100.24; var_dump($float_val); // Strings $str = "String $int_val"; $str1 = 'String $int_val'; var_dump($str); var_dump($str1); // Arrays $arr = [1, 3, 4, 5, 6]; var_dump($arr); $arr2 = array(1, 3, 4, 5, 6); var_dump($arr2); $arr3[1] = 100; var_dump($arr3); // Objects class Person { public $name = "123"; } $person = new Person(); var_dump($person); // Special types $test = NULL; var_dump($test); $fd = fopen('./abc.txt', 'r'); var_dump($fd); ?> \n## Type Conversion and Operators php"><?php // Type conversion $num = 100; $float_val = 20.01; var_dump($num + $float_val); $bool = true; $num2 = 10; var_dump($bool + $num2); $bool2 = false; var_dump($bool2 + $num2); $str = "100.01aaaa"; $num3 = 10; var_dump($str + $num3); $bool3 = true; $str2 = "10abc"; var_dump($bool3 + $str2); // Explicit type conversion $str = "101abc"; var_dump(intval($str)); var_dump(floatval($str)); var_dump(boolval($str)); $num4 = 100; var_dump(boolval($num4)); // Type checking $bool4 = true; $str3 = "abcdef"; var_dump(is_bool($bool4)); var_dump(is_bool($str3)); // Arithmetic operators $num5 = 100; $num6 = 50; var_dump($num5 + $num6); var_dump($num5 - $num6); var_dump($num5 * $num6); var_dump($num5 / $num6); var_dump($num5 % 3); var_dump($num5 + $num6 * 2); var_dump(($num5 + $num6) * 2); $num5++; var_dump($num5); $num5--; var_dump($num5); // String operators $name = "John"; $age = 23; echo "Name: ". $name . " Age: ". $age; echo $name . $age; // Assignment operators $name = "John Doe"; var_dump($name); $num = 100; $num += 100; var_dump($num); $num -= 50; var_dump($num); $num *= 2; var_dump($num); $num /= 3; var_dump($num); $num %= 3; var_dump($num); $str = "John Doe"; $str .= " Age 23"; var_dump($str); // Comparison operators $num = 100; $num1 = 200; var_dump($num > $num1); var_dump($num < $num1); var_dump($num >= 100); var_dump($num <= 100); var_dump($num == $num1); var_dump($num == 100); $str = "100aaa"; var_dump($num == $str); var_dump($num === $str); // Ternary operator var_dump(100 > 2 ? "True" : "False"); var_dump(100 < 2 ? "True" : "False"); var_dump($num < $num1 ? "True" : "False"); // Logical operators var_dump(1 > 2 and 3 > 1); var_dump(2 > 1 and 3 > 2); var_dump(1 > 2 or 3 > 1); var_dump(2 > 1 or 3 > 2); var_dump(2 < 1 or 3 < 2); var_dump(!(1 > 2)); var_dump(!(2 > 1)); ?> \n## Control Structures php"><?php // Sequential structure echo "1"; echo "2"; echo "3"; // Conditional structure if (1 < 2) { echo "Condition met"; } echo "<br>"; if (2 < 1) { echo "Condition not met"; } echo "<br>"; // Two-way branch if (2 > 3) { echo "Condition met"; } else { echo "Condition not met"; } echo "<br>"; $age = 17; if ($age >= 18) { echo "Play freely"; } else { echo "Under 18, limit playtime"; } echo "<br>"; // Multi-branch $age = 35; if ($age < 18) { echo "Under 18, limit playtime"; } elseif ($age <= 30) { echo "Play freely"; } elseif ($age <= 50) { echo "Consider spending some money!"; } else { echo "Take care of your health, go to bed early!"; } echo "Branches end!"; // Loop structures for ($i = 0; $i < 10; $i++) { echo $i . "<br>"; } // Nested loops for ($i = 1; $i < 10; $i++) { for ($j = 1; $j <= $i; $j++) { echo $i . "*" . $j . "=" . ($i * $j) . " "; } echo "<br>"; } $num = 1; while ($num <= 10) { $num++; if ($num == 5) { continue; } echo $num; } $num = 1; do { echo "do-while loop"; echo $num; } while ($num > 10); $arr = ['a', 'b', 'c', 'd', 'e', 'f']; foreach ($arr as $k => $v) { echo "Key: ". $k . " Value: ". $v . "<br>"; } ?> \n## Functions php"><?php // Function declaration function func() { echo "I am a function<br>"; } echo "Outside function body"; // Function call echo "Before function call<br>"; func(); echo "After function call<br>"; // Parameters and return values function func1($num, $num2) { echo $num + $num2; } $num = 100; func1($num, 200); // Return value function func2($num, $num1) { return $num + $num1; } $result = func2(100, 200); var_dump($result); // Default parameters function func3($num, $num2 = 100) { return $num + $num2; } $num = 110; $result = func3($num); var_dump($result); $result = func3($num, 500); var_dump($result); // Scope $name = "John Doe"; function func4() { $realname = "Jane Doe"; var_dump("Real name inside function: ". $realname); } function func5() { $num = 100; var_dump("Num inside function: ". $num); } function func6() { global $name; var_dump("Name in func6: ". $name); $name = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"; } func4(); func5(); func6(); var_dump("Name outside: ". $name); // Static variables function func7() { static $num = 1; $num++; echo "<br>"; var_dump($num); } func7(); func7(); func7(); func7(); func7(); // Variable functions $func_name = "func7"; $func_name(); ?> \n## Arrays php"><?php // Array initialization $arr = array('dong', '18', 'Security Expert'); $arr1[] = 'x'; echo $arr[2]; echo $arr1[0]; // Output: Security Expert x var_dump($arr); // Array traversal for ($i = 0; $i < count($arr); $i++) { echo $arr[$i] . '<hr />'; } // Associative array $arr = array('name' => 'dong', 'age' => '18', 'profession' => 'Security Expert'); foreach ($arr as $key => $value) { echo 'Key: ' . $key . ' Value: ' . $value . '<br />'; } // Multidimensional array $arr = array('name' => 'dong', 'age' => '18', 'profession' => array('Security', 'Network Engineering')); foreach ($arr as $key => $value) { if (is_array($value)) { foreach ($value as $k1 => $v1) { echo 'Nested array'; } } else { echo 'Key: ' . $key . ' Value: ' . $value . '<br />'; } } ?> \n## Timestamps php"><?php // Timestamp $timestamp = time(); echo $timestamp . '<hr />'; echo date('Y-m-d H:i:s', $timestamp); // Output: 1591749201 2020-06-10 08:33:21 ?> \n## GET and POST Requests php"><?php // GET request var_dump($_GET); // Write GET parameter to file $l = $_GET['mumu']; $m = fopen("./22.txt", "w"); fwrite($m, $l); ?> \n## Ternary Operator php"><?php // Ternary operator example $a = 1 ? "2343" : "300"; // Outputs 2343 $a = isset($_GET['name']) ? '1000' : $_GET['name']; echo $a; ?>