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@ -6,15 +6,8 @@ author_url: http://emarref.net/
This document describes PHP 5+.
## [Basic Syntax](http://www.php.net/manual/en/language.basic-syntax.php)
All statements must end with a semi-colon; All PHP code must be between <?php and ?> tags. PHP can also be
configured to respect the [short open tags](http://www.php.net/manual/en/ini.core.php#ini.short-open-tag) <? and ?>.
## [Comments](http://www.php.net/manual/en/language.basic-syntax.comments.php)
```php
<?php
<?php // PHP code must be enclosed with <?php ? > tags
// Two forward slashes start a one-line comment.
@ -24,27 +17,36 @@ configured to respect the [short open tags](http://www.php.net/manual/en/ini.cor
Surrounding text in slash-asterisk and asterisk-slash
makes it a multi-line comment.
*/
```
## [Types](http://www.php.net/manual/en/language.types.php)
// Use "echo" or "print" to print output
print('Hello '); // Prints "Hello " with no line break
Types are [weakly typed](http://en.wikipedia.org/wiki/Strong_and_weak_typing) and begin with the $ symbol.
A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.
// () are optional for print and echo
echo 'World\n'; // Prints "World" with a line break
// (all statements must end with a semicolon)
### Scalars
```php
// Anything outside <?php tags is echoed automatically
?>Hello World Again!
<?php
/************************************
* Types & Variables
*/
// Variables begin with the $ symbol.
// A valid variable name starts with a letter or underscore,
// followed by any number of letters, numbers, or underscores.
// Boolean values are case-insensitive
$boolean = true; // or TRUE or True
$boolean = false; // or FALSE or False
// Integers
$integer = 1234; // decimal number
$integer = -123; // a negative number
$integer = 0123; // octal number (equivalent to 83 decimal)
$integer = 0x1A; // hexadecimal number (equivalent to 26 decimal)
$int1 = 19; // => 19
$int2 = -19; // => -19
$int3 = 019; // => 15 (a leading 0 denotes an octal number)
$int4 = 0x0F; // => 15 (a leading 0x denotes a hex literal)
// Floats (aka doubles)
$float = 1.234;
@ -52,28 +54,30 @@ $float = 1.2e3;
$float = 7E-10;
// Arithmetic
$sum = $number + $float;
$difference = $number - $float;
$product = $number * $float;
$quotient = $number / $float;
$sum = 1 + 1; // 2
$difference = 2 - 1; // 1
$product = 2 * 2; // 4
$quotient = 2 / 1; // 2
// Shorthand arithmetic
$number = 0;
$number += 1; // Add 1 to $number
$number++; // Add 1 to $number after it is used
++$number; // Add 1 to $number before it is used.
$number /= $float // Divide and assign the quotient to $number
echo $number++; // Prints 1 (increments after evaluation)
echo ++$number; // Prints 3 (increments before evalutation)
$number /= $float; // Divide and assign the quotient to $number
// Strings should be enclosed in single quotes;
$sgl_quotes = '$String'; // => '$String'
// Avoid using double quotes except to embed other variables
$dbl_quotes = "This is a $sgl_quotes." // => 'This is a $String'
$dbl_quotes = "This is a $sgl_quotes."; // => 'This is a $String'
// Escape special characters with backslash
// Special characters are only escaped in double quotes
$escaped = "This contains a \t tab character.";
$unescaped = 'This just contains a slash and a t: \t';
// Enclose a variable in curly braces if needed
$money = "I have $${integer} in the bank."
$money = "I have $${number} in the bank.";
// Since PHP 5.3, nowdocs can be used for uninterpolated multi-liners
$nowdoc = <<<'END'
@ -81,35 +85,40 @@ Multi line
string
END;
// Heredocs will do string interpolation
$heredoc = <<<END
Multi line
$sgl_quotes
END; // Nowdoc syntax is available in PHP 5.3.0
END;
// Manipulation
$concatenated = $sgl_quotes . $dbl_quotes;
```
// String concatenation is done with .
echo 'This string ' . 'is concatenated';
### Compound
```php
<?php
/********************************
* Arrays
*/
// Arrays
$array = array(1, 2, 3);
$array = [1, 2, 3]; // As of PHP 5.4
$string = ["One", "Two", "Three"];
$string[0]; // Holds the value "One";
// All arrays in PHP are associative arrays (hashmaps),
// Associative arrays, known as hashmaps in some languages.
$associative = ["One" => 1, "Two" => 2, "Three" => 3];
$associative["One"]; // Holds the value 1
```
## Output
// Works with all PHP versions
$associative = array('One' => 1, 'Two' => 2, 'Three' => 3);
```php
<?php
// PHP 5.4 introduced a new syntax
$associative = ['One' => 1, 'Two' => 2, 'Three' => 3];
echo $associative['One']; // prints "1"
// List literals implicitly assign integer keys
$array = ['One', 'Two', 'Three'];
echo $array[0]; // => "One"
/********************************
* Output
*/
echo('Hello World!');
// Prints Hello World! to stdout.
@ -121,133 +130,127 @@ print('Hello World!'); // The same as echo
echo 'Hello World!';
print 'Hello World!'; // So is print
$paragraph = 'paragraph';
echo 100;
echo $variable;
echo function_result();
echo $paragraph;
// If short open tags are configured, or your PHP version is
// 5.4.0 or greater, you can use the short echo syntax
<?= $variable ?>
```
## [Operators](http://www.php.net/manual/en/language.operators.php)
### Assignment
```php
?>
<p><?= $paragraph ?></p>
<?php
$x = 1;
$y = 2;
$x = $y; // A now contains the same value sa $y
$x = &$y;
$z = &$y;
// $x now contains a reference to $y. Changing the value of
// $x will change the value of $y also, and vice-versa.
```
### Comparison
echo $x; // => 2
echo $z; // => 2
$y = 0;
echo $x; // => 2
echo $z; // => 0
```php
<?php
/********************************
* Logic
*/
$a = 0;
$b = '0';
$c = '1';
$d = '1';
// assert throws a warning if its argument is not true
// These comparisons will always be true, even if the types aren't the same.
$a == $b // TRUE if $a is equal to $b after type juggling.
$a != $b // TRUE if $a is not equal to $b after type juggling.
$a <> $b // TRUE if $a is not equal to $b after type juggling.
$a < $b // TRUE if $a is strictly less than $b.
$a > $b // TRUE if $a is strictly greater than $b.
$a <= $b // TRUE if $a is less than or equal to $b.
$a >= $b // TRUE if $a is greater than or equal to $b.
assert($a == $b); // equality
assert($b != $a); // inequality
assert($a <> $b); // alternative inequality
assert($a < $c);
assert($c > $b);
assert($a <= $b);
assert($c >= $d);
// The following will only be true if the values match and are the same type.
$a === $b // TRUE if $a is equal to $b, and they are of the same type.
$a !== $b // TRUE if $a is not equal to $b, or they are not of the same type.
1 == '1' // TRUE
1 === '1' // FALSE
```
assert($c === $d);
assert($a !== $d);
assert(1 == '1');
assert(1 !== '1');
## [Type Juggling](http://www.php.net/manual/en/language.types.type-juggling.php)
Variables can be converted between types, depending on their usage.
```php
<?php
// Variables can be converted between types, depending on their usage.
$integer = 1;
echo $integer + $integer; // Outputs 2;
echo $integer + $integer; // => 2
$string = '1';
echo $string + $string;
// Also outputs 2 because the + operator converts the strings to integers
echo $string + $string; // => 2 (strings are coerced to integers)
$string = 'one';
echo $string + $string;
echo $string + $string; // => 0
// Outputs 0 because the + operator cannot cast the string 'one' to a number
```
Type casting can be used to treat a variable as another type temporarily by using cast operators in parentheses.
// Type casting can be used to treat a variable as another type
```php
$boolean = (boolean) $integer; // $boolean is true
$boolean = (boolean) 1; // => true
$zero = 0;
$boolean = (boolean) $zero; // $boolean is false
$boolean = (boolean) $zero; // => false
// There are also dedicated functions for casting most types
$integer = 5;
$string = strval($integer);
// There are also dedicated functions for casting most types
$var = null; // Null value
```
## [Control Structures](http://www.php.net/manual/en/language.control-structures.php)
### If Statements
/********************************
* Control Structures
*/
```php
<?php
if (/* test */) {
// Do something
if (true) {
print 'I get printed';
}
if (/* test */) {
// Do something
if (false) {
print "I don't";
} else {
// Do something else
print 'I get printed';
}
if (/* test */) {
// Do something
} elseif(/* test2 */) {
// Do something else, only if test2
if (false) {
print 'Does not get printed';
} elseif(true) {
print 'Does';
}
if (/* test */) {
// Do something
} elseif(/* test2 */) {
// Do something else, only if test2
$x = 0;
if ($x === '0') {
print 'Does not print';
} elseif($x == '1') {
print 'Does not print';
} else {
// Do something default
print 'Does print';
}
// This alternative syntax is useful for templates:
?>
<?php if (/* test */): ?>
<?php if ($x): ?>
This is displayed if the test is truthy.
<?php else: ?>
This is displayed otherwise.
<?php endif; ?>
```
### Switch statements
```php
<?php
switch ($variable) {
case 'one':
// Do something if $variable == 'one'
break;
// Use switch to save some logic.
switch ($x) {
case '0':
print 'Switch does type coercion';
break; // You must include a break, or you will fall through
case 'two':
case 'three':
// Do something if $variable is either 'two' or 'three'
@ -256,106 +259,98 @@ switch ($variable) {
// Do something by default
}
```
### Loops
```php
<?php
// While, do...while and for loops are probably familiar
$i = 0;
while ($i < 5) {
echo $i++;
}
}; // Prints "01234"
echo "\n";
$i = 0;
do {
echo $i++;
} while ($i < 5);
} while ($i < 5); // Prints "01234"
echo "\n";
for ($x = 0; $x < 10; $x++) {
echo $x; // Will echo 0 - 9
}
}// Prints "0123456789"
$wheels = ["bicycle" => 2, "car" => 4];
echo "\n";
$wheels = ['bicycle' => 2, 'car' => 4];
// Foreach loops can iterate over arrays
foreach ($wheels as $wheel_count){
echo "$wheel_count";
} // Prints "24"
echo "\n";
// You can iterate over the keys as well as the values
foreach ($wheels as $vehicle => $wheel_count) {
echo "A $vehicle has $wheel_count wheels";
}
// This loop will stop after outputting 2
echo "\n";
$i = 0;
while ($i < 5) {
if ($i == 3) {
break; // Exit out of the while loop and continue.
if ($i === 3) {
break; // Exit out of the while loop
}
echo $i++;
}
}// Prints "012"
// This loop will output everything except 3
$i = 0;
while ($i < 5) {
if ($i == 3) {
for($i = 0; $i < 5; $i++){
if ($i === 3) {
continue; // Skip this iteration of the loop
}
echo $i++;
}
```
echo $i;
} // Prints "0124"
## Functions
Functions are created with the ```function``` keyword.
/********************************
* Functions
*/
```php
<?php
function my_function($my_arg) {
$my_variable = 1;
// Define a function with "function":
function my_function() {
return 'Hello';
}
// $my_variable and $my_arg cannot be accessed outside of the function
```
echo my_function(); // => "Hello"
Functions may be invoked by name.
// A valid function name starts with a letter or underscore, followed by any
// number of letters, numbers, or underscores.
```php
<?php
my_function_name();
$variable = get_something(); // A function may return a value
```
A valid function name starts with a letter or underscore, followed by any
number of letters, numbers, or underscores. There are three ways to declare functions.
### [User-defined](http://www.php.net/manual/en/functions.user-defined.php)
```php
<?php
function my_function_name ($arg_1, $arg_2) {
// $arg_1 and $arg_2 are required
function add($x, $y = 1) { // $y is optional, and defaults to 2
$result = $x + $y;
return $result;
}
// Functions may be nested to limit scope
function outer_function ($arg_1 = null) { // $arg_1 is optional
function inner_function($arg_2 = 'two') { // $arg_2 will default to 'two'
}
}
echo add(4); // => 5
echo add(4, 2); // => 6
// inner_function() does not exist and cannot be called until
// outer_function() is called
```
// $result is not accessible outside the function
// print $result; // Gives a warning.
This enables [currying](http://en.wikipedia.org/wiki/Currying) in PHP.
// Since PHP 5.3 you can declare anonymous functions;
$inc = function($x){
return $x + 1;
};
echo $inc(2); // => 3
```php
function foo ($x, $y, $z) {
echo "$x - $y - $z";
}
// Functions can return functions
function bar ($x, $y) {
// Use 'use' to bring in outside variables
return function ($z) use ($x, $y) {
foo($x, $y, $z);
};
@ -363,92 +358,77 @@ function bar ($x, $y) {
$bar = bar('A', 'B');
$bar('C');
```
### [Variable](http://www.php.net/manual/en/functions.variable-functions.php)
// You can call named functions using strings
$function_name = 'add';
echo $function_name(1, 2); // => 3
// But, you should probably use anonymous functions instead.
```php
<?php
/********************************
* Classes
*/
$function_name = 'my_function_name';
$function_name(); // will execute the my_function_name() function
```
### [Anonymous](http://www.php.net/manual/en/functions.anonymous.php)
Similar to variable functions, functions may be anonymous.
```php
<?php
function my_function($callback) {
$callback('My argument');
}
my_function(function ($my_argument) {
// do something
});
// Closure style
$my_function = function() {
// Do something
};
$my_function();
```
## [Classes](http://www.php.net/manual/en/language.oop5.php)
Classes are defined with the ```class``` keyword.
```php
<?php
//Classes are defined with the class keyword
class MyClass {
const MY_CONST = 'value';
static $staticVar = 'something';
public $property = 'value'; // Properties must declare their visibility
}
const MY_CONST = 'value'; // A constant
static $staticVar = 'static';
public $property = 'public'; // Properties must declare their visibility
private $privprop = 'private'; // Accessible within the class only
protected $protprop = 'protected'; // Accessible within the class and subclasses
public $instanceProp;
echo MyClass::MY_CONST; // Outputs "value";
final class YouCannotExtendMe {
}
```
Classes are instantiated with the ```new``` keyword. Functions are referred to as
methods if they belong to a class.
```php
<?php
class MyClass {
function myFunction() {
// Create a constructor with __construct
public function __construct($instanceProp){
// Access instance variables with $this
$this->instanceProp = $instanceProp;
}
// Methods are declared as functions inside a class
public function myMethod() {
print "MyClass";
}
final function youCannotOverrideMe() {
}
public static function myStaticMethod() {
print "I am static";
}
}
$cls = new MyClass(); // The parentheses are optional.
echo MyClass::MY_CONST; // Outputs "value";
echo MyClass::$staticVar; // Outputs 'static';
MyClass::myStaticMethod(); // Outputs "I am static";
echo MyClass::$staticVar; // Access to static vars
// Access class members using ->.
$my_class = new MyClass("An instance property"); // The parentheses are optional.
echo $my_class->property; // => "public"
echo $my_class->instanceProp; // => "An instance property"
$my_class->myMethod(); // => "MyClass"
echo $cls->property; // Access to properties
MyClass::myStaticMethod(); // myStaticMethod cannot be run on $cls
```
// Extend classes using "extends"
class MyOtherClass extends MyClass{
function printProtectedProperty(){
echo $this->protprop;
}
PHP offers some [magic methods](http://www.php.net/manual/en/language.oop5.magic.php) for classes.
// Override a method
function myMethod() {
parent::myMethod();
print " > MyOtherClass";
}
}
```php
<?php
$my_other_class = new MyOtherClass("Instance prop");
$my_other_class->printProtectedProperty(); // => Prints "protected"
$my_other_class->myMethod(); // Prints "MyClass > MyOtherClass"
class MyClass {
final class YouCannotExtendMe {
}
// You can use "magic methods" to create getters and setters
class MyMapClass {
private $property;
public function __get($key)
@ -462,16 +442,13 @@ class MyClass {
}
}
$x = new MyClass();
$x = new MyMapClass();
echo $x->property; // Will use the __get() method
$x->property = 'Something'; // Will use the __set() method
```
Classes can be abstract (using the ```abstract``` keyword), extend other classes (using the ```extends``` keyword) and
implement interfaces (using the ```implements``` keyword). An interface is declared with the ```interface``` keyword.
```php
<?php
// Classes can be abstract (using the abstract keyword) or
// implement interfaces (using the implements keyword).
// An interface is declared with the interface keyword.
interface InterfaceOne
{
@ -480,90 +457,105 @@ interface InterfaceOne
interface InterfaceTwo
{
public function doSomething();
public function doSomethingElse();
}
abstract class MyAbstractClass implements InterfaceOne
{
public $x = "doSomething";
}
class MyClass extends MyAbstractClass implements InterfaceTwo
class MyConcreteClass extends MyAbstractClass implements InterfaceTwo
{
public function doSomething(){
echo $x;
}
public function doSomethingElse(){
echo "doSomethingElse";
}
}
// Classes can implement more than one interface
class SomeOtherClass implements InterfaceOne, InterfaceTwo
{
public function doSomething(){
echo "doSomething";
}
public function doSomethingElse(){
echo "doSomethingElse";
}
}
/********************************
* Traits
*/
//Traits are available since PHP 5.4.0 and are declared using the trait keyword.
trait MyTrait {
public function myTraitMethod()
{
print "I have MyTrait";
}
}
class MyTraitfulClass
{
use MyTrait;
}
$cls = new MyTraitfulClass();
$cls->myTraitMethod(); // Prints "I have MyTrait"
/********************************
* Namespaces
*/
// This section is separate, because a namespace declaration
// must be the first statement in a file. Let's pretend that is not the case
/*
```
### [Namespaces](http://www.php.net/manual/en/language.namespaces.rationale.php)
By default, classes exist in the global namespace, and can be explicitly called with a backslash.
```php
<?php
// By default, classes exist in the global namespace, and can
// be explicitly called with a backslash.
$cls = new \MyClass();
```
```php
<?php
// Set the namespace for a file
namespace My\Namespace;
class MyClass
{
}
// (from another file)
$cls = new My\Namespace\MyClass;
```
Or from within another namespace.
```php
<?php
//Or from within another namespace.
namespace My\Other\Namespace;
use My\Namespace\MyClass;
$cls = new MyClass();
```
Or you can alias the namespace;
```php
<?php
// Or you can alias the namespace;
namespace My\Other\Namespace;
use My\Namespace as SomeOtherNamespace;
$cls = new SomeOtherNamespace\MyClass();
```
### [Traits](http://www.php.net/manual/en/language.oop5.traits.php)
*/
Traits are available since PHP 5.4.0 and are declared using the ```trait``` keyword.
```php
<?php
trait MyTrait {
public function myTraitMethod()
{
// Do something
}
}
class MyClass
{
use MyTrait;
}
$cls = new MyClass();
$cls->myTraitMethod();
```
## More Information