Useful PHP Predefined Constants defined by the PHP core.

PHP_VERSION - Contains a string with the current PHP version.
echo PHP_VERSION; // 5.5.3
PHP_MAXPATHLEN - The maximum length of filenames (including path) supported by this build of PHP.
echo PHP_MAXPATHLEN; // 260
PHP_OS - Contains a string that can be used to detect the operatig system PHP is running on. Some posible values:
CYGWIN_NT-5.1, Darwin (for Mac Os X), FreeBSD, HP-UX, IRIX64, Linux, NetBSD, OpenBSD, SunOS, Unix, WIN32, WINNT (for Windows NT), Windows, CYGWIN_NT-5.1, IRIX64, SunOS, HP-UX, OpenBSD.
echo PHP_OS; // WINNT
PHP_EOL - The correct 'End Of Line' symbol for the platform on which PHP is running on. Useful to add new lines in strings.
echo 'http://coursesweb.net/'. PHP_EOL .'Next line';
__LINE__ - The current line number of the file.
<?php
// test
echo __LINE__;       // 3
__FILE__ - The full path and filename of the current php file. If used inside an include, the name of the included file is returned.
echo __FILE__; // D:\server\www\file.php
__DIR__ - The directory of the current php file. If used inside an include, the directory of the included file is returned. This is equivalent to: dirname(__FILE__). Not have a trailing slash unless it is the root directory.
echo __DIR__; // D:\server\www
__FUNCTION__ - The function name in which this constant is accessed.
function someName() {
  echo __FUNCTION__;
}
someName();      // someName
__CLASS__ - Returns the class name as it was declared (case-sensitive).
class someClass {
  public function className() {
    return __CLASS__;
  }
}

$obj = new someClass();
echo $obj->className();      // someClass
__METHOD__ - Returns the class method name as it was declared, including the class name (case-sensitive).
class someClass {
  public function someMethod() {
    return __METHOD__;
  }
}

$obj = new someClass();
echo $obj->someMethod();      // someClass::someMethod

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which tag is used in <table> to create table header cell?
<thead> <th> <td>
<table><tr>
  <th>Title 1</th>
  <th>Title 2</th>
</tr></table>
Which CSS property sets the distance between lines?
line-height word-spacing margin
.some_class {
  line-height: 150%;
}
Which function opens a new browser window.
alert() confirm() open()
document.getElementById("id_button").onclick = function(){
  window.open("http://coursesweb.net/");
}
Indicate the PHP function that returns an array with names of the files and folders inside a directory.
mkdir() scandir() readdir()
$ar_dir = scandir("dir_name");
var_export($ar_dir);
PHP Predefined Constants

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