PHP/Language Basics/Variables
Содержание
- 1 A properly set-up PHP variable
- 2 Automatic Type Conversion
- 3 Calculate the variable name for simpler variables and use that name to access the value of that variable.
- 4 Numbers
- 5 Numeric Data Types
- 6 Operating on variables
- 7 PHP 5 variable functionality.
- 8 PHP Superglobal Arrays
- 9 PHP Variable Examples
- 10 Valid and invalid variable names
- 11 valid statements
A properly set-up PHP variable
<source lang="html4strict">
<?php
$myvar = 0; $yourvar = "This is my value
"; $myvar = $yourvar; $myvar = "This is now my value.
"; echo $yourvar; $myvar = &$yourvar; $myvar = "This is now my value.
"; echo $yourvar;
?>
</source>
Automatic Type Conversion
<source lang="html4strict">
<?
$mystring = "12"; $myinteger = 20; print $mystring + $myinteger;
?>
</source>
Calculate the variable name for simpler variables and use that name to access the value of that variable.
<source lang="html4strict">
<?php $a0 = "This"; $a1 = "is"; $a2 = "a"; $a3 = "test"; for ($i = 0; $i < 4; $i++) {
$var = "a$i"; echo "${$var} ";
} ?>
</source>
Numbers
<source lang="html4strict">
<?
print 6; print 6.3; print 6.30; print 0.4422; print 16.216; print 0; print -23; print 1298317; print -9912111; print -12.52222; print 0.00;
?>
</source>
Numeric Data Types
<source lang="html4strict">
<?php $a = 5; $b = $a / 2; echo "$a / 2 = $b\n";
$a = 6; $b = $a / 2; echo "$a / 2 = $b\n"; ?>
</source>
Operating on variables
<source lang="html4strict">
<?php $price = 3.95; $tax_rate = 0.08; $tax_amount = $price * $tax_rate; $total_cost = $price + $tax_amount; $username = "james"; $domain = "@example.ru"; $email_address = $username . $domain; print "The tax is " . $tax_amount; print "\n"; // this prints a linebreak print "The total cost is " .$total_cost; print "\n"; // this prints a linebreak print $email_address; ?>
</source>
PHP 5 variable functionality.
<source lang="html4strict">
<?php
$myvar = 0; $yourvar = "This is my value
"; $myvar = $yourvar; $myvar = "This is now my value.
"; echo $yourvar; $myvar = &$yourvar; $myvar = "This is now my value.
"; echo $yourvar; $formvar = $_POST["formvar"]; if ($_SESSION["loggedin"]){ echo "Proper login"; } else { echo "You are not logged in."; }
?>
</source>
PHP Superglobal Arrays
<source lang="html4strict">
Array Description
$_COOKIE Contains keys and values set as browser cookies
$_ENV Contains keys and values set by the script"s shell context
$_FILES Contains information about uploaded files
$_GET Contains keys and values submitted to the script using the HTTP get method
$_POST Contains keys and values submitted to the script using the HTTP post method
$_REQUEST A combined array containing values from the $_GET, $_POST, and $_COOKIES superglobal arrays
$_SERVER Variables made available by the server
$GLOBALS Contains all global variables associated with the current script
</source>
PHP Variable Examples
<source lang="html4strict">
<?php
$myvar = "foo"; /* Assigns the string "foo" */ $php5 = "is cool"; /* Correct Syntax */
?>
</source>
Valid and invalid variable names
<source lang="html4strict">
$myvar Correct
$Name Correct
$_Age Correct
$___AGE___ Correct
$9 Incorrect ; starts with a number
$1Name Incorrect ; starts with a number
$Name1 Correct; numbers are fine at the end and after the first character
$_Name1 Correct
$Name"s Incorrect; no symbols other than "_" are allowed
</source>
valid statements
<source lang="html4strict">
<?php
$number = "5"; # $number is a string $sum = 15 + $number; # Add an integer and string to produce integer $sum = "twenty"; # Overwrite $sum with a string.
?>
</source>