(PHP 4 >= 4.1.0, PHP 5, PHP 7) Server and execution environment information $_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server. There is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. That said, a large number of these variables are accounted for in the » CGI/1.1 specificati

Examples: The Built in Exception class A User defined Exception class can be defined by extending the built-in Exception class. The members and properties below, show what is accessible within the child class that derives from the built-in Exception class. <?php class Exception {     protected $message = 'Unknown exception';   // exception message     private   $string;                          // __toString cache     protected $code = 0;                        /

(PHP 5 >= 5.5.0, PHP 7) Examples: Implementing range() as a generator Generators provide an easy way to implement simple iterators without the overhead or complexity of implementing a class that implements the Iterator interface. A generator allows you to write code that uses foreach to iterate over a set of data without needing to build an array in memory, which may cause you to exce

(PHP 5 >= 5.3.0, PHP 7) Examples: Name resolutions illustrated <?php namespace A; use B\D, C\E as F; // function calls foo();      // first tries to call "foo" defined in namespace "A"             // then calls global function "foo" \foo();     // calls function "foo" defined in global scope my\foo();   // calls function "foo" defined in namespace "A\my" F();        // first tr

(PHP 5 >= 5.3.0, PHP 7) Examples: Using global space specification Without any namespace definition, all class and function definitions are placed into the global space - as it was in PHP before namespaces were supported. Prefixing a name with \ will specify that the name is required from the global space even in the context of the namespace. <?php namespace A\B\C; /* This functi

(PHP 5 >= 5.3.0, PHP 7) Examples: Accessing global classes inside a namespace Inside a namespace, when PHP encounters an unqualified Name in a class name, function or constant context, it resolves these with different priorities. Class names always resolve to the current namespace name. Thus to access internal or non-namespaced user classes, one must refer to them with their fully quali

Examples: The primary advantage of generators is their simplicity. Much less boilerplate code has to be written compared to implementing an Iterator class, and the code is generally much more readable. For example, the following function and class are equivalent: <?php function getLinesFromFile($fileName) {     if (!$fileHandle = fopen($fileName, 'r')) {         return;     }       while (false !== $line = fgets($fileHandle)) {         yield $line;     }       f

Examples: A simple example of yielding values The heart of a generator function is the yield keyword. In its simplest form, a yield statement looks much like a return statement, except that instead of stopping execution of the function and returning, yield instead provides a value to the code looping over the generator and pauses execution of the generator function. <?php function gen_one_to_three() {     for ($i = 1; $i <= 3; $i++) {         // Note that $i i

(PHP 4, PHP 5, PHP 7) References all variables available in global scope An associative array containing references to all variables which are currently defined in the global scope of the script. The variable names are the keys of the array. Notes: This is a 'superglobal', or automatic global, variable. This simply means that it is available in all scopes throughout a script. The

(PHP 5 >= 5.3.0, PHP 7) Examples: Declaring a single namespace with hierarchy Much like directories and files, PHP namespaces also contain the ability to specify a hierarchy of namespace names. Thus, a namespace name can be defined with sub-levels: <?php namespace MyProject\Sub\Level; const CONNECT_OK = 1; class Connection { /* ... */ } function connect() { /* ... */  } ?>