mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 09:41:36 +00:00
Adam Bard
commit
534c5dcb93
474
php.html.markdown
Normal file
474
php.html.markdown
Normal file
@ -0,0 +1,474 @@
|
||||
---
|
||||
language: php
|
||||
author: Malcolm Fell
|
||||
author_url: http://emarref.net/
|
||||
---
|
||||
|
||||
# PHP
|
||||
|
||||
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
|
||||
// Two forward slashes start a one-line comment.
|
||||
|
||||
# So will a hash (aka pound symbol) but // is more common
|
||||
|
||||
/*
|
||||
Surrounding text in slash-asterisk and asterisk-slash
|
||||
makes it a multi-line comment.
|
||||
*/
|
||||
```
|
||||
|
||||
## [Types](http://www.php.net/manual/en/language.types.php)
|
||||
|
||||
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.
|
||||
|
||||
### Scalars
|
||||
|
||||
```php
|
||||
// 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)
|
||||
|
||||
// Floats (aka doubles)
|
||||
$float = 1.234;
|
||||
$float = 1.2e3;
|
||||
$float = 7E-10;
|
||||
|
||||
// Arithmetic
|
||||
$sum = $number + $float;
|
||||
$difference = $number - $float;
|
||||
$product = $number * $float;
|
||||
$quotient = $number / $float;
|
||||
|
||||
// Shorthand arithmetic
|
||||
$number += 1; // Will add 1 to $number
|
||||
$number++; // Will add 1 to $number after it is used
|
||||
++$number; // Will add 1 to $number before it is used.
|
||||
$number /= $float // Will divide $number $float, and assign the quotient to $number
|
||||
|
||||
// Strings
|
||||
$sgl_quotes = 'String'; // Strings should be enclosed in single quotes;
|
||||
$dbl_quotes = "This is a $sgl_quotes." // Avoid using double quotes to embed other variables
|
||||
$escaped = "This contains a \t tab character."; // Escape special characters with backslash
|
||||
$money = "I have $${integer} in the bank." // Enclose a variable in curly braces if needed
|
||||
$nowdoc = <<<'END'
|
||||
Multi line
|
||||
string
|
||||
END;
|
||||
$heredoc = <<<END
|
||||
Multi line
|
||||
$sgl_quotes
|
||||
END; // Nowdoc syntax is available in PHP 5.3.0
|
||||
|
||||
// Manipulation
|
||||
$concatinated = $sgl_quotes + $dbl_quotes;
|
||||
```
|
||||
|
||||
### Compound
|
||||
|
||||
```php
|
||||
// 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";
|
||||
|
||||
// Associative arrays, known as hashmaps in some languages.
|
||||
$associative = ["One" => 1, "Two" => 2, "Three" => 3];
|
||||
$associative["One"]; // Holds the value 1
|
||||
```
|
||||
|
||||
## Output
|
||||
|
||||
```php
|
||||
echo('Hello World!'); // Prints Hello World! to stdout. Stdout is the web page if running in a browser.
|
||||
print('Hello World!'); // The same as echo
|
||||
echo 'Hello World!'; // echo is actually a language construct, so you can drop the parentheses.
|
||||
echo 100;
|
||||
echo $variable;
|
||||
echo function_result(); // Output the result of a function call that returns a value. More on functions later.
|
||||
|
||||
// If [short open tags](http://www.php.net/manual/en/ini.core.php#ini.short-open-tag) 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
|
||||
$a = 1;
|
||||
$b = 2;
|
||||
$a = $b; // A now contains the same value sa $b
|
||||
$a =& $b; // A now contains a reference to $b. Changing the value of $a will change the value of $b also, and vice-versa.
|
||||
```
|
||||
|
||||
### Comparison
|
||||
|
||||
```php
|
||||
$a == $b // TRUE if $a is equal to $b after type juggling.
|
||||
$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 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, or they are not of the same type.
|
||||
$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.
|
||||
```
|
||||
|
||||
## [Type Juggling](http://www.php.net/manual/en/language.types.type-juggling.php)
|
||||
|
||||
Variables can be converted between types, depending on their usage.
|
||||
|
||||
```php
|
||||
$integer = 1;
|
||||
echo $integer + $integer; // Outputs 2;
|
||||
|
||||
$string = '1';
|
||||
echo $string + $string; // Also outputs 2 because the + operator converts the strings to integers
|
||||
|
||||
$string = 'one';
|
||||
echo $string + $string; // Outputs 0 because the + operator cannot cast the string 'one' to a number
|
||||
|
||||
$boolean = (boolean) $integer; // $boolean is true
|
||||
|
||||
$zero = 0;
|
||||
$boolean = (boolean) $zero; // $boolean is false
|
||||
|
||||
$integer = 5;
|
||||
$string = strval($integer); // There are also dedicated functions for casting most types
|
||||
|
||||
$var = null; // Null value
|
||||
```
|
||||
|
||||
## [Control Structures](http://www.php.net/manual/en/language.control-structures.php)
|
||||
|
||||
### If Statements
|
||||
|
||||
```php
|
||||
if (/* test */) {
|
||||
// Do something
|
||||
}
|
||||
|
||||
if (/* test */) {
|
||||
// Do something
|
||||
} else {
|
||||
// Do something else
|
||||
}
|
||||
|
||||
if (/* test */) {
|
||||
// Do something
|
||||
} elseif(/* test2 */) {
|
||||
// Do something else, only if test2
|
||||
}
|
||||
|
||||
if (/* test */) {
|
||||
// Do something
|
||||
} elseif(/* test2 */) {
|
||||
// Do something else, only if test2
|
||||
} else {
|
||||
// Do something default
|
||||
}
|
||||
|
||||
<?php if (/* test */): ?>
|
||||
<!-- Do something that isn't PHP -->
|
||||
<?php else: ?>
|
||||
<!-- Do something default -->
|
||||
<?php endif; ?>
|
||||
```
|
||||
|
||||
### Switch statements
|
||||
|
||||
```php
|
||||
switch ($variable) {
|
||||
case 'one':
|
||||
// Do something if $variable == 'one'
|
||||
break;
|
||||
case 'two':
|
||||
case 'three':
|
||||
// Do something if $variable is either 'two' or 'three'
|
||||
break;
|
||||
default:
|
||||
// Do something by default
|
||||
}
|
||||
|
||||
```
|
||||
|
||||
### Loops
|
||||
|
||||
```php
|
||||
$i = 0;
|
||||
while ($i < 5) {
|
||||
echo $i++;
|
||||
}
|
||||
|
||||
$i = 0;
|
||||
do {
|
||||
echo $i++;
|
||||
} while ($i < 5);
|
||||
|
||||
for ($x = 0; $x < 10; $x++) {
|
||||
echo $x; // Will echo 0 - 9
|
||||
}
|
||||
|
||||
$wheels = ["bicycle" => 2, "car" => 4];
|
||||
|
||||
foreach ($wheels as $vehicle => $wheel_count) {
|
||||
echo "A $vehicle has $wheel_count wheels";
|
||||
}
|
||||
|
||||
// This loop will stop after outputting 2
|
||||
$i = 0;
|
||||
while ($i < 5) {
|
||||
if ($i == 3) {
|
||||
break; // Exit out of the while loop and continue.
|
||||
}
|
||||
|
||||
echo $i++;
|
||||
}
|
||||
|
||||
// This loop will output everything except 3
|
||||
$i = 0;
|
||||
while ($i < 5) {
|
||||
if ($i == 3) {
|
||||
continue; // Skip this iteration of the loop
|
||||
}
|
||||
|
||||
echo $i++;
|
||||
}
|
||||
```
|
||||
|
||||
## Functions
|
||||
|
||||
Functions are created with the ```function``` keyword.
|
||||
|
||||
```php
|
||||
function my_function($my_arg) {
|
||||
$my_variable = 1;
|
||||
}
|
||||
|
||||
// $my_variable and $my_arg cannot be accessed outside of the function
|
||||
```
|
||||
|
||||
Functions may be invoked by name.
|
||||
|
||||
```php
|
||||
my_function_name();
|
||||
|
||||
$variable = get_something(); // A function may return a value
|
||||
```
|
||||
|
||||
A valid function name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. There are three ways to declare functions.
|
||||
|
||||
### [User-defined](http://www.php.net/manual/en/functions.user-defined.php)
|
||||
|
||||
```php
|
||||
function my_function_name ($arg_1, $arg_2) { // $arg_1 and $arg_2 are required
|
||||
// Do something with $arg_1 and $arg_2;
|
||||
}
|
||||
|
||||
// Functions may be nested to limit scope
|
||||
function outer_function ($arg_1 = null) { // $arg_1 is optional
|
||||
function inner_function($arg_2 = 'two') { // $arg_2 will default to 'two'
|
||||
}
|
||||
}
|
||||
|
||||
// inner_function() does not exist and cannot be called until outer_function() is called
|
||||
```
|
||||
|
||||
### [Variable](http://www.php.net/manual/en/functions.variable-functions.php)
|
||||
|
||||
```php
|
||||
$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
|
||||
my_function(function () {
|
||||
// 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
|
||||
class MyClass {
|
||||
const MY_CONST = 'value';
|
||||
static $staticVar = 'something';
|
||||
public $property = 'value'; // Properties must declare their visibility
|
||||
}
|
||||
|
||||
echo MyClass::MY_CONST; // Outputs "value";
|
||||
|
||||
final class YouCannotExtendMe {
|
||||
}
|
||||
```
|
||||
|
||||
Classes are insantiated with the ```new``` keyword. Functions are referred to as methods if they belong to a class.
|
||||
|
||||
```php
|
||||
class MyClass {
|
||||
function myFunction() {
|
||||
}
|
||||
|
||||
function function youCannotOverrideMe()
|
||||
{
|
||||
}
|
||||
|
||||
public static function myStaticMethod()
|
||||
{
|
||||
}
|
||||
}
|
||||
|
||||
$cls = new MyClass(); // The parentheses are optional.
|
||||
|
||||
echo MyClass::$staticVar; // Access to static vars
|
||||
|
||||
echo $cls->property; // Access to properties
|
||||
|
||||
MyClass::myStaticMethod(); // myStaticMethod cannot be run on $cls
|
||||
```
|
||||
|
||||
PHP offers some [magic methods](http://www.php.net/manual/en/language.oop5.magic.php) for classes.
|
||||
|
||||
```php
|
||||
class MyClass {
|
||||
private $property;
|
||||
|
||||
public function __get($key)
|
||||
{
|
||||
return $this->$key;
|
||||
}
|
||||
|
||||
public function __set($key, $value)
|
||||
{
|
||||
$this->$key = $value;
|
||||
}
|
||||
}
|
||||
|
||||
$x = new MyClass();
|
||||
echo $x->property; // Will use the __get() method to retrieve the value of $property
|
||||
$x->property = 'Something'; // Will use the __set() method to set the value of property
|
||||
```
|
||||
|
||||
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
|
||||
interface InterfaceOne
|
||||
{
|
||||
public function doSomething();
|
||||
}
|
||||
|
||||
interface InterfaceTwo
|
||||
{
|
||||
public function doSomething();
|
||||
}
|
||||
|
||||
abstract class MyAbstractClass implements InterfaceOne
|
||||
{
|
||||
}
|
||||
|
||||
class MyClass extends MyAbstractClass implements InterfaceTwo
|
||||
{
|
||||
}
|
||||
|
||||
// Classes can implement more than one interface
|
||||
class SomeOtherClass implements InterfaceOne, InterfaceTwo
|
||||
{
|
||||
}
|
||||
```
|
||||
|
||||
### [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
|
||||
$cls = new \MyClass();
|
||||
```
|
||||
|
||||
```php
|
||||
namespace My\Namespace;
|
||||
|
||||
class MyClass
|
||||
{
|
||||
}
|
||||
|
||||
$cls = new My\Namespace\MyClass;
|
||||
```
|
||||
|
||||
Or from within another namespace.
|
||||
|
||||
```php
|
||||
namespace My\Other\Namespace;
|
||||
|
||||
use My\Namespace\MyClass;
|
||||
|
||||
$cls = new MyClass();
|
||||
```
|
||||
|
||||
Or you can alias the namespace;
|
||||
|
||||
```php
|
||||
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
|
||||
trait MyTrait {
|
||||
public function myTraitMethod()
|
||||
{
|
||||
// Do something
|
||||
}
|
||||
}
|
||||
|
||||
class MyClass
|
||||
{
|
||||
use MyTrait;
|
||||
}
|
||||
|
||||
$cls = new MyClass();
|
||||
$cls->myTraitMethod();
|
||||
```
|
||||
|
||||
## More Information
|
||||
|
||||
Visit the [official PHP documentation](http://www.php.net/manual/) for reference and community input.
|
||||
|
||||
If you're interested in up-to-date best practices, visit [PHP The Right Way](http://www.phptherightway.com/).
|
||||
|
||||
If you're coming from a language with good package management, check out [Composer](http://getcomposer.org/).
|
||||
Loading…
Reference in New Issue
Block a user