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Si vous êtes nouveau au PHP ou devez juste régénérer vos qualifications, c'est l'endroit à commencer. Cette série de cours d'instruction te donnera la connaissance de base que vous devrez créer un simple Site Web de PHP.
Le PHP est un langage de programmation r3fléchissant à l'origine conçu pour produire les pages Web dynamiques. [1] Le PHP est employé principalement dans le serveur-côté scripting, mais peut être employé d'une ligne de commande interface ou dans des applications graphiques autonomes. Des interfaces utilisateurs textuelles peuvent également être créées utilisant des ncurses.
Floating point numbers (also known as "floats", "doubles", or "real numbers") can be specified using any of the following syntaxes:
<?php
$a = 1.234;
$b = 1.2e3;
$c = 7E-10;
?>
Formally:
LNUM [0-9]+
DNUM ([0-9]*[\.]{LNUM}) | ({LNUM}[\.][0-9]*)
EXPONENT_DNUM (({LNUM} | {DNUM}) [eE][+-]? {LNUM})
The size of a float is platform-dependent, although a maximum of ~1.8e308 with a precision of roughly 14 decimal digits is a common value (the 64 bit IEEE format).
It is typical that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9.
This is due to the fact that it is impossible to express some fractions in decimal notation with a finite number of digits. For instance, 1/3 in decimal form becomes 0.3.
So never trust floating number results to the last digit, and never compare floating point numbers for equality. If higher precision is necessary, the arbitrary precision math functions and gmp functions are available.
For information on converting strings to float, see String conversion to numbers. For values of other types, the conversion is performed by converting the value to integer first and then to float. See Converting to integer for more information. As of PHP 5, a notice is thrown if an object is converted to float.