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JavaScript et PHP - Comparaisons à l'apprentissage  

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JavaScript et PHP - Comparaisons à l\'apprentissage Cet article énumère JavaScript certaines comparaisons entre deux langages de programmation web les plus populaires dans le monde de l'open source: JavaScript et PHP. Variables, Objet et Array, Structure de contrôle s; dans cette liste, les programmeurs web (les programmeurs) jetez un oeil à leur sujet plus précis et donner les solutions mai appropriative pour les besoins de leurs missions.


Étiquette: PHP, Comparaison, langage de programmation, Programmation Web, Variable, Objet, Array, Structure de contrôle, codeur web, Programmeur Web, exigence, tâche, solution

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This is a basic comparison between PHP and JavaScript. It's intended for users familiar with PHP and looking for JavaScript equivalents.

JavaScript and PHP Comparisons:

Variables

Variable Scope

PHP and JavaScript take two very different approaches to declaring variables. In PHP, all variables are local in scope unless declared as global. JavaScript is opposite, and all variables are global unless declared with the var keyword.

PHP

<?php
function foo() {
  $variable_a = 'value'; // Local variable declaration.
}
function bar() {
  print $variable_a; // Prints nothing.
}

function foo() {
  global $variable_b; // Global variable declaration.
  $variable_b = 'value';
}
function bar() {
  global $variable_b;
  print $variable_b; // Prints 'value'.
}
?>

JavaScript

function foo() {
  var variableA = 'value'; // Local variable with use of "var".
}
function bar() {
  alert(variableA); // Variable not defined error.
}

function foo() {
  variableB = 'value'; // Global variable, no "var" declaration.
}
function bar() {
  alert(variableB); // alert('value')
}

An interesting twist is JavaScript also allows scoping within functions. When using the "var" declaration, variables are available for everything in the current function or any sub-functions.

PHP

function foo() {
  $variable_a = 'value'; // Local variable declaration.
  function bar() {
    print $variable_a; // Prints nothing.
  }
}

JavaScript

function foo() {
  var variableA = 'value'; // Local variable with use of "var".
  function bar() {
    alert(variableA); // alert('value');
  }
}

Variable Types

Both PHP and JavaScript are loosely typed, meaning a variable can be of any type, and change from one type to another. However both PHP and JavaScript keep track of the type of variables, and you can check this type.

PHP

<?php
$foo = 3;
is_int($foo); // TRUE

$foo = '3';
is_int($foo); // FALSE
is_string($foo); // TRUE
?>

JavaScript

var foo = 3;
type_of(foo); // 'number'

foo = '3';
type_of(foo); // 'string'

Casting Variables

Every now and then you might need to cast variables to a specific type. This is extremely important when dealing with JavaScript's + operator, which is used for both string concatenation and for numeric addition.

PHP
In PHP, variables may be cast to certain type by using parenthesis. String concatenation is done with "." and addition with "+".

<?php
$foo = '3.5 kg';
$bar = (float)$foo; // 3.5
$bar = (int)$foo; // 3
$baz = (string)$foo; // '3.5 kg'

print $bar + $baz; // 6
print $bar . $baz; // '33'
?>

JavaScript
JavaScript has functions specifically for casting variables to numbers. Both string concatenation and addition is done with "+". If mixing a string and a number with "+", concatenation will take precedence over addition.

var foo = '3.5 kg';
var bar = parseFloat(foo); // 3.5
    bar = parseInt(foo); // 3
var baz = '3';

alert(bar + baz); // '33'
alert(bar + parseInt(baz)); // 6

Checking for NULL or empty() values

Variables in PHP don't have to be defined for you to use them, though if you're working with E_ALL compliance on (not the default of most PHP installs), your script will throw a notice if you try to use an undeclared variable. JavaScript is a bit mixed concerning undeclared variables, if you attempt to modify or compare with an undeclared variable, the script will break entirely, but you can check the variable status using typeof() or in conditional statements containing only that variable.

PHP

<?php
// Check if a variable is declared at all.
if (!isset($foo)) {
  $foo = TRUE;
}

// Or check if a variable has a value that equates to FALSE.
// This includes variables that have not been declared.
if (empty($bar)) {
  $bar = TRUE;
}
?>

JavaScript

// Check if a variable is declared at all.
if (typeof(foo) == 'undefined') {
  var foo = true;
}

// Or check if a variable has a value that equates to false.
// This includes variables that have not been declared.
if (!bar) {
  var bar = true;
}

// However an undeclared variable can't be used in comparisons.
if (baz == false) { // Variable undefined error.
  var baz = true;
}

Boolean Variables

A simple but important thing to remember is that JavaScript only recognizes the keyword true in all lowercase. PHP accepts both uppercase and lowercase.

PHP

<?php
is_boolean(TRUE); // TRUE
is_boolean(true); // TRUE
is_boolean(True); // TRUE
?>

JavaScript

typeof(true); // 'boolean'
typeof(TRUE); // 'undefined'
typeof(True); // 'undefined'

Case Sensitivity

Both JavaScript and PHP are case sensitive in their variables. PHP is not case-sensitive in function or class declarations, but JavaScript is case sensitive for these also.

PHP

<?php
// Variable case:
$foo = 'bar';
print $foo; // Prints 'bar'.
print $Foo; // Prints nothing.

// Function case:
function foo() {
  print 'bar';
}
foo(); // Prints 'bar'.
Foo(); // Prints 'bar'.
?>

JavaScript

// Variable case:
var foo = 'bar';
alert(foo); // alert('bar')
alert(Foo); // Variable not defined error.

// Function case:
function foo() {
  alert('bar');
}
foo(); // alert('bar')
Foo(); // Function not defined error.
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JavaScript et PHP - Comparaisons à l'apprentissage - Langue: Française 0/5 0 votes / 46,386 previews / 0 commentaire 02/06/2010 Cet article énumère JavaScript certaines comparaisons entre deux langages de programmation web les plus populaires dan...JavaScript et PHP - Comparaisons à l'apprentissage - JavaScript et PHP - Comparaisons à l'apprentissage - Langue: Française

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