PHP

<?php
echo "gethostbyname('localhost'): " . gethostbyname("localhost") . "<br>";
echo "gethostbyaddr('127.0.0.1'): " . gethostbyaddr("127.0.0.1") . "<br>";
echo "ip2long('192.168.1.10'): " . ip2long("192.168.1.10") . "<br>";
echo "long2ip(3232235786): " . long2ip(3232235786) . "<br>";
echo "getservbyname('http', 'tcp'): " . getservbyname("http", "tcp") . "<br>";
echo "getservbyname('https', 'tcp'): " . getservbyname("https", "tcp") . "<br>";
echo "getservbyport(3306, 'tcp'): " . getservbyport(3306, "tcp") . "<br>";
echo "getprotobyname('tcp'): " . getprotobyname("tcp") . "<br>";

// open a socket to the local web server and send a raw HTTP request
$fp = fsockopen("localhost", 80, $errno, $errstr, 5);
if (!$fp) {
    echo "Socket error: $errstr ($errno)";
} else {
    fwrite($fp, "HEAD / HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n");
    echo "First line of the server's reply: " . fgets($fp);
    fclose($fp);
}
?>

<?php
ob_start();
echo "This text goes into the buffer.";
$captured = ob_get_contents();
$length = ob_get_length();
ob_end_clean();                          // discard the buffer – nothing was sent
echo "Captured: '$captured' ($length characters)<br>";

function shout($buffer) { return strtoupper($buffer); }
ob_start("shout");                       // pass the output through a callback
echo "this line is converted to capitals by the callback.<br>";
ob_end_flush();

ob_start();
include "box.php";                       // capture the output of an included file
$html = ob_get_clean();
echo "box.php produced " . strlen($html) . " bytes: " . $html;
echo "<br>Buffer level now: " . ob_get_level();
?>

<?php
echo "phpversion(): " . phpversion() . "<br>";
echo "zend_version(): " . zend_version() . "<br>";
echo "php_sapi_name(): " . php_sapi_name() . "<br>";
echo "php_uname('s'): " . php_uname("s") . "<br>";
echo "version_compare(PHP_VERSION, '8.0.0', '>='): " . var_export(version_compare(PHP_VERSION, "8.0.0", ">="), true) . "<br>";
echo "ini_get('upload_max_filesize'): " . ini_get("upload_max_filesize") . "<br>";
echo "ini_get('max_execution_time'): " . ini_get("max_execution_time") . "<br>";
ini_set("max_execution_time", "60");
echo "after ini_set: " . ini_get("max_execution_time") . ", get_cfg_var: " . get_cfg_var("max_execution_time") . "<br>";
echo "extension_loaded('mysqli'): " . var_export(extension_loaded("mysqli"), true) . "<br>";
echo "Number of loaded extensions: " . count(get_loaded_extensions()) . "<br>";
echo "mysqli functions: " . count(get_extension_funcs("mysqli")) . "<br>";
echo "Memory used: " . round(memory_get_usage() / 1024) . " KB<br>";
echo "Script owner: " . get_current_user() . ", PID: " . (getmypid() > 0 ? "a number" : "?") . "<br>";
echo "M_PI constant: " . get_defined_constants(true)['standard']['M_PI'];
?>

<?php
session_name("PHPBOOKSESS");
session_start();
$_SESSION['user'] = "Asha";
$_SESSION['role'] = "student";
echo "session_status(): " . (session_status() === PHP_SESSION_ACTIVE ? "PHP_SESSION_ACTIVE" : "other") . "<br>";
echo "session_name(): " . session_name() . "<br>";
echo "session_id() length: " . strlen(session_id()) . " characters<br>";
echo "session_encode(): " . session_encode() . "<br>";
$p = session_get_cookie_params();
echo "cookie lifetime: {$p['lifetime']}, path: {$p['path']}, httponly: " . var_export($p['httponly'], true) . "<br>";
$old = session_id();
session_regenerate_id(true);
echo "Id changed after regenerate: " . var_export($old !== session_id(), true) . "<br>";
session_unset();
echo "After session_unset, items in \$_SESSION: " . count($_SESSION) . "<br>";
session_destroy();
echo "After session_destroy: " . (session_status() === PHP_SESSION_NONE ? "PHP_SESSION_NONE" : "active");
?>