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+---
+language: PHP
+contributors:
+ - ["Malcolm Fell", "http://emarref.net/"]
+ - ["Trismegiste", "https://github.com/Trismegiste"]
+translators:
+ - ["Mario Pérez", "https://github.com/MarioPerezEsteso"]
+lang: es-es
+filename: learnphp-es.php
+---
+
+This document describes PHP 5+.
+
+```php
+<?php // PHP code must be enclosed with <?php tags
+
+// If your php file only contains PHP code, it is best practice
+// to omit the php closing tag to prevent accidental output.
+
+// 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.
+*/
+
+// Use "echo" or "print" to print output
+print('Hello '); // Prints "Hello " with no line break
+
+// () are optional for print and echo
+echo "World\n"; // Prints "World" with a line break
+// (all statements must end with a semicolon)
+
+// 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
+$int1 = 12; // => 12
+$int2 = -12; // => -12
+$int3 = 012; // => 10 (a leading 0 denotes an octal number)
+$int4 = 0x0F; // => 15 (a leading 0x denotes a hex literal)
+
+// Floats (aka doubles)
+$float = 1.234;
+$float = 1.2e3;
+$float = 7E-10;
+
+// Delete variable
+unset($int1);
+
+// Arithmetic
+$sum = 1 + 1; // 2
+$difference = 2 - 1; // 1
+$product = 2 * 2; // 4
+$quotient = 2 / 1; // 2
+
+// Shorthand arithmetic
+$number = 0;
+$number += 1; // Increment $number by 1
+echo $number++; // Prints 1 (increments after evaluation)
+echo ++$number; // Prints 3 (increments before evaluation)
+$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 $String.'
+
+// Special characters are only escaped in double quotes
+$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 $${number} in the bank.";
+
+// Since PHP 5.3, nowdocs can be used for uninterpolated multi-liners
+$nowdoc = <<<'END'
+Multi line
+string
+END;
+
+// Heredocs will do string interpolation
+$heredoc = <<<END
+Multi line
+$sgl_quotes
+END;
+
+// String concatenation is done with .
+echo 'This string ' . 'is concatenated';
+
+// Strings can be passed in as parameters to echo
+echo 'Multiple', 'Parameters', 'Valid'; // Returns 'MultipleParametersValid'
+
+
+/********************************
+ * Constants
+ */
+
+// A constant is defined by using define()
+// and can never be changed during runtime!
+
+// a valid constant name starts with a letter or underscore,
+// followed by any number of letters, numbers, or underscores.
+define("FOO", "something");
+
+// access to a constant is possible by calling the choosen name without a $
+echo FOO; // Returns 'something'
+echo 'This outputs '.FOO; // Returns 'This ouputs something'
+
+
+
+/********************************
+ * Arrays
+ */
+
+// All arrays in PHP are associative arrays (hashmaps),
+
+// Associative arrays, known as hashmaps in some languages.
+
+// Works with all PHP versions
+$associative = array('One' => 1, 'Two' => 2, 'Three' => 3);
+
+// PHP 5.4 introduced a new syntax
+$associative = ['One' => 1, 'Two' => 2, 'Three' => 3];
+
+echo $associative['One']; // prints 1
+
+// List literals implicitly assign integer keys
+$array = ['One', 'Two', 'Three'];
+echo $array[0]; // => "One"
+
+// Add an element to the end of an array
+$array[] = 'Four';
+// or
+array_push($array, 'Five');
+
+// Remove element from array
+unset($array[3]);
+
+/********************************
+ * Output
+ */
+
+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 and print are language constructs too, so you can drop the parentheses
+echo 'Hello World!';
+print 'Hello World!';
+
+$paragraph = 'paragraph';
+
+echo 100; // Echo scalar variables directly
+echo $paragraph; // or variables
+
+// If short open tags are configured, or your PHP version is
+// 5.4.0 or greater, you can use the short echo syntax
+?>
+<p><?= $paragraph ?></p>
+<?php
+
+$x = 1;
+$y = 2;
+$x = $y; // $x now contains the same value as $y
+$z = &$y;
+// $z now contains a reference to $y. Changing the value of
+// $z will change the value of $y also, and vice-versa.
+// $x will remain unchanged as the original value of $y
+
+echo $x; // => 2
+echo $z; // => 2
+$y = 0;
+echo $x; // => 2
+echo $z; // => 0
+
+// Dumps type and value of variable to stdout
+var_dump($z); // prints int(0)
+
+// Prints variable to stdout in human-readable format
+print_r($array); // prints: Array ( [0] => One [1] => Two [2] => Three )
+
+/********************************
+ * Logic
+ */
+$a = 0;
+$b = '0';
+$c = '1';
+$d = '1';
+
+// assert throws a warning if its argument is not true
+
+// These comparisons will always be true, even if the types aren't the same.
+assert($a == $b); // equality
+assert($c != $a); // inequality
+assert($c <> $a); // alternative inequality
+assert($a < $c);
+assert($c > $b);
+assert($a <= $b);
+assert($c >= $d);
+
+// The following will only be true if the values match and are the same type.
+assert($c === $d);
+assert($a !== $d);
+assert(1 === '1');
+assert(1 !== '1');
+
+// 'Spaceship' operator (since PHP 7)
+// Returns 0 if values on either side are equal
+// Returns 1 if value on the left is greater
+// Returns -1 if the value on the right is greater
+
+$a = 100;
+$b = 1000;
+
+echo $a <=> $a; // 0 since they are equal
+echo $a <=> $b; // -1 since $a < $b
+echo $b <=> $a; // 1 since $b > $a
+
+// Variables can be converted between types, depending on their usage.
+
+$integer = 1;
+echo $integer + $integer; // => 2
+
+$string = '1';
+echo $string + $string; // => 2 (strings are coerced to integers)
+
+$string = 'one';
+echo $string + $string; // => 0
+// Outputs 0 because the + operator cannot cast the string 'one' to a number
+
+// Type casting can be used to treat a variable as another type
+
+$boolean = (boolean) 1; // => true
+
+$zero = 0;
+$boolean = (boolean) $zero; // => false
+
+// There are also dedicated functions for casting most types
+$integer = 5;
+$string = strval($integer);
+
+$var = null; // Null value
+
+
+/********************************
+ * Control Structures
+ */
+
+if (true) {
+ print 'I get printed';
+}
+
+if (false) {
+ print 'I don\'t';
+} else {
+ print 'I get printed';
+}
+
+if (false) {
+ print 'Does not get printed';
+} elseif(true) {
+ print 'Does';
+}
+
+// ternary operator
+print (false ? 'Does not get printed' : 'Does');
+
+// ternary shortcut operator since PHP 5.3
+// equivalent of "$x ? $x : 'Does'""
+$x = false;
+print($x ?: 'Does');
+
+// null coalesce operator since php 7
+$a = null;
+$b = 'Does print';
+echo $a ?? 'a is not set'; // prints 'a is not set'
+echo $b ?? 'b is not set'; // prints 'Does print'
+
+
+$x = 0;
+if ($x === '0') {
+ print 'Does not print';
+} elseif($x == '1') {
+ print 'Does not print';
+} else {
+ print 'Does print';
+}
+
+
+
+// This alternative syntax is useful for templates:
+?>
+
+<?php if ($x): ?>
+This is displayed if the test is truthy.
+<?php else: ?>
+This is displayed otherwise.
+<?php endif; ?>
+
+<?php
+
+// Use switch to save some logic.
+switch ($x) {
+ case '0':
+ print 'Switch does type coercion';
+ break; // You must include a break, or you will fall through
+ // to cases 'two' and 'three'
+ case 'two':
+ case 'three':
+ // Do something if $variable is either 'two' or 'three'
+ break;
+ default:
+ // Do something by default
+}
+
+// While, do...while and for loops are probably familiar
+$i = 0;
+while ($i < 5) {
+ echo $i++;
+}; // Prints "01234"
+
+echo "\n";
+
+$i = 0;
+do {
+ echo $i++;
+} while ($i < 5); // Prints "01234"
+
+echo "\n";
+
+for ($x = 0; $x < 10; $x++) {
+ echo $x;
+} // Prints "0123456789"
+
+echo "\n";
+
+$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 $wheel_count wheels";
+}
+
+echo "\n";
+
+$i = 0;
+while ($i < 5) {
+ if ($i === 3) {
+ break; // Exit out of the while loop
+ }
+ echo $i++;
+} // Prints "012"
+
+for ($i = 0; $i < 5; $i++) {
+ if ($i === 3) {
+ continue; // Skip this iteration of the loop
+ }
+ echo $i;
+} // Prints "0124"
+
+
+/********************************
+ * Functions
+ */
+
+// Define a function with "function":
+function my_function () {
+ return 'Hello';
+}
+
+echo my_function(); // => "Hello"
+
+// A valid function name starts with a letter or underscore, followed by any
+// number of letters, numbers, or underscores.
+
+function add ($x, $y = 1) { // $y is optional and defaults to 1
+ $result = $x + $y;
+ return $result;
+}
+
+echo add(4); // => 5
+echo add(4, 2); // => 6
+
+// $result is not accessible outside the function
+// print $result; // Gives a warning.
+
+// Since PHP 5.3 you can declare anonymous functions;
+$inc = function ($x) {
+ return $x + 1;
+};
+
+echo $inc(2); // => 3
+
+function foo ($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, $z);
+ };
+}
+
+$bar = bar('A', 'B');
+$bar('C'); // Prints "A - B - C"
+
+// You can call named functions using strings
+$function_name = 'add';
+echo $function_name(1, 2); // => 3
+// Useful for programatically determining which function to run.
+// Or, use call_user_func(callable $callback [, $parameter [, ... ]]);
+
+
+// You can get the all the parameters passed to a function
+function parameters() {
+ $numargs = func_num_args();
+ if ($numargs > 0) {
+ echo func_get_arg(0) . ' | ';
+ }
+ $args_array = func_get_args();
+ foreach ($args_array as $key => $arg) {
+ echo $key . ' - ' . $arg . ' | ';
+ }
+}
+
+parameters('Hello', 'World'); // Hello | 0 - Hello | 1 - World |
+
+// Since PHP 5.6 you can get a variable number of arguments
+function variable($word, ...$list) {
+ echo $word . " || ";
+ foreach ($list as $item) {
+ echo $item . ' | ';
+ }
+}
+
+variable("Separate", "Hello", "World") // Separate || Hello | World |
+
+/********************************
+ * Includes
+ */
+
+<?php
+// PHP within included files must also begin with a PHP open tag.
+
+include 'my-file.php';
+// The code in my-file.php is now available in the current scope.
+// If the file cannot be included (e.g. file not found), a warning is emitted.
+
+include_once 'my-file.php';
+// If the code in my-file.php has been included elsewhere, it will
+// not be included again. This prevents multiple class declaration errors
+
+require 'my-file.php';
+require_once 'my-file.php';
+// Same as include(), except require() will cause a fatal error if the
+// file cannot be included.
+
+// Contents of my-include.php:
+<?php
+
+return 'Anything you like.';
+// End file
+
+// Includes and requires may also return a value.
+$value = include 'my-include.php';
+
+// Files are included based on the file path given or, if none is given,
+// the include_path configuration directive. If the file isn't found in
+// the include_path, include will finally check in the calling script's
+// own directory and the current working directory before failing.
+/* */
+
+/********************************
+ * Classes
+ */
+
+// Classes are defined with the class keyword
+
+class MyClass
+{
+ const MY_CONST = 'value'; // A constant
+
+ static $staticVar = 'static';
+
+ // Static variables and their visibility
+ public static $publicStaticVar = 'publicStatic';
+ // Accessible within the class only
+ private static $privateStaticVar = 'privateStatic';
+ // Accessible from the class and subclasses
+ protected static $protectedStaticVar = 'protectedStatic';
+
+ // Properties must declare their visibility
+ public $property = 'public';
+ public $instanceProp;
+ protected $prot = 'protected'; // Accessible from the class and subclasses
+ private $priv = 'private'; // Accessible within the class only
+
+ // Create a constructor with __construct
+ public function __construct($instanceProp) {
+ // Access instance variables with $this
+ $this->instanceProp = $instanceProp;
+ }
+
+ // Methods are declared as functions inside a class
+ public function myMethod()
+ {
+ print 'MyClass';
+ }
+
+ //final keyword would make a function unoverridable
+ final function youCannotOverrideMe()
+ {
+ }
+
+/*
+ * Declaring class properties or methods as static makes them accessible without
+ * needing an instantiation of the class. A property declared as static can not
+ * be accessed with an instantiated class object (though a static method can).
+ */
+
+ public static function myStaticMethod()
+ {
+ print 'I am static';
+ }
+}
+
+// Class constants can always be accessed statically
+echo MyClass::MY_CONST; // Outputs 'value';
+
+echo MyClass::$staticVar; // Outputs 'static';
+MyClass::myStaticMethod(); // Outputs 'I am static';
+
+// Instantiate classes using new
+$my_class = new MyClass('An instance property');
+// The parentheses are optional if not passing in an argument.
+
+// Access class members using ->
+echo $my_class->property; // => "public"
+echo $my_class->instanceProp; // => "An instance property"
+$my_class->myMethod(); // => "MyClass"
+
+
+// Extend classes using "extends"
+class MyOtherClass extends MyClass
+{
+ function printProtectedProperty()
+ {
+ echo $this->prot;
+ }
+
+ // Override a method
+ function myMethod()
+ {
+ parent::myMethod();
+ print ' > MyOtherClass';
+ }
+}
+
+$my_other_class = new MyOtherClass('Instance prop');
+$my_other_class->printProtectedProperty(); // => Prints "protected"
+$my_other_class->myMethod(); // Prints "MyClass > MyOtherClass"
+
+final class YouCannotExtendMe
+{
+}
+
+// You can use "magic methods" to create getters and setters
+class MyMapClass
+{
+ private $property;
+
+ public function __get($key)
+ {
+ return $this->$key;
+ }
+
+ public function __set($key, $value)
+ {
+ $this->$key = $value;
+ }
+}
+
+$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) or
+// implement interfaces (using the implements keyword).
+// An interface is declared with the interface keyword.
+
+interface InterfaceOne
+{
+ public function doSomething();
+}
+
+interface InterfaceTwo
+{
+ public function doSomethingElse();
+}
+
+// interfaces can be extended
+interface InterfaceThree extends InterfaceTwo
+{
+ public function doAnotherContract();
+}
+
+abstract class MyAbstractClass implements InterfaceOne
+{
+ public $x = 'doSomething';
+}
+
+class MyConcreteClass extends MyAbstractClass implements InterfaceTwo
+{
+ public function doSomething()
+ {
+ echo $x;
+ }
+
+ public function doSomethingElse()
+ {
+ echo 'doSomethingElse';
+ }
+}
+
+
+// Classes can implement more than one interface
+class SomeOtherClass implements InterfaceOne, InterfaceTwo
+{
+ public function doSomething()
+ {
+ echo 'doSomething';
+ }
+
+ public function doSomethingElse()
+ {
+ echo 'doSomethingElse';
+ }
+}
+
+
+/********************************
+ * Traits
+ */
+
+// Traits are available from PHP 5.4.0 and are declared using "trait"
+
+trait MyTrait
+{
+ public function myTraitMethod()
+ {
+ print 'I have MyTrait';
+ }
+}
+
+class MyTraitfulClass
+{
+ use MyTrait;
+}
+
+$cls = new MyTraitfulClass();
+$cls->myTraitMethod(); // Prints "I have MyTrait"
+
+
+/********************************
+ * Namespaces
+ */
+
+// This section is separate, because a namespace declaration
+// must be the first statement in a file. Let's pretend that is not the case
+
+<?php
+
+// By default, classes exist in the global namespace, and can
+// be explicitly called with a backslash.
+
+$cls = new \MyClass();
+
+
+
+// Set the namespace for a file
+namespace My\Namespace;
+
+class MyClass
+{
+}
+
+// (from another file)
+$cls = new My\Namespace\MyClass;
+
+//Or from within another namespace.
+namespace My\Other\Namespace;
+
+use My\Namespace\MyClass;
+
+$cls = new MyClass();
+
+// Or you can alias the namespace;
+
+namespace My\Other\Namespace;
+
+use My\Namespace as SomeOtherNamespace;
+
+$cls = new SomeOtherNamespace\MyClass();
+
+
+/**********************
+* Late Static Binding
+*
+*/
+
+class ParentClass {
+ public static function who() {
+ echo "I'm a " . __CLASS__ . "\n";
+ }
+ public static function test() {
+ // self references the class the method is defined within
+ self::who();
+ // static references the class the method was invoked on
+ static::who();
+ }
+}
+
+ParentClass::test();
+/*
+I'm a ParentClass
+I'm a ParentClass
+*/
+
+class ChildClass extends ParentClass {
+ public static function who() {
+ echo "But I'm " . __CLASS__ . "\n";
+ }
+}
+
+ChildClass::test();
+/*
+I'm a ParentClass
+But I'm ChildClass
+*/
+
+
+/**********************
+* Error Handling
+*
+*/
+
+// Simple error handling can be done with try catch block
+
+try {
+ // Do something
+} catch (Exception $e) {
+ // Handle exception
+}
+
+// When using try catch blocks in a namespaced enviroment use the following
+
+try {
+ // Do something
+} catch (\Exception $e) {
+ // Handle exception
+}
+
+// Custom exceptions
+
+class MyException extends Exception {}
+
+try {
+
+ $condition = true;
+
+ if ($condition) {
+ throw new MyException('Something just happend');
+ }
+
+} catch (MyException $e) {
+ // Handle my exception
+}
+
+```
+
+## 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/).
+
+For common standards, visit the PHP Framework Interoperability Group's
+[PSR standards](https://github.com/php-fig/fig-standards).