__LINE__     The current line number of the file.
__FILE__    The full path and filename of the file. If used inside an include, the name of the included file is returned. Since PHP 4.0.2, __FILE__ always contains an absolute path whereas in older versions it contained relative path under some circumstances.
__FUNCTION__    The function name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the function name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.
__CLASS__   The class name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the class name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.
__METHOD__  The class method name. (Added in PHP 5.0.0) The method name is returned as it was declared (case-sensitive).



if ($handle = opendir('.')) {
    while (false !== ($file = readdir($handle))) {
        if ($file != "." && $file != "..") {
            echo "$file\n";
        }
    }
    closedir($handle);
}



// This prints out that "they are the same"
if ($fst === $str) {
    echo "they are the same";
}


if (is_int($an_int)) {
    $an_int += 4;
}


if (is_string($a_bool)) {
    echo "String: $a_bool";
}


$GLOBALS

$_SERVER

$_GET

$_POST

$_COOKIE

$_FILES

$_ENV

$_REQUEST

$_SESSION


$new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES);
echo $new; // &lt;a href=&#039;test&#039;&gt;Test&lt;/a&gt;
s

$str = "A 'quote' is <b>bold</b>";

// Outputs: A 'quote' is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str);

// Outputs: A &#039;quote&#039; is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str, ENT_QUOTES);


$query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar);
echo '<a href="mycgi?' . htmlentities($query_string) . '">';