Variables in PHP
A variable is an area of memory which is set aside
to store information , this is assigned an identifier
by the programmer . You can recognise variables in PHP
because they are prefixed with the dollar ( $ ) sign
. To assign a variable you use the assignment operator
( = ) . Here is an example of this.
$name = "iain hendry";
$intDaysInWeek = 7;
In the first example the variable identifier in this
example is $name and the string value "iain hendry"
has been assigned to it . In the second example the
variable identifier is $intDaysInWeek and the number
7 is assigned to it . Note that in the number example
we do not surround the variable with quotes in this
way PHP treats this as a numeric value but if we had
put quotes round it then PHP would have treated it as
a string.
Variable Naming
There are some guidelines to follow for naming variables
in PHP and these are as follows .
1. All variable names must begin with a letter or underscore
character .
2 . The name of the variable can be made up of numbers
, letters , underscores but you cant use charcters like
+ , - , & , £ , * , etc
One important thing to note if you are coming from another
programming language there is no size limit for
variables .
Case Sensitivity
One thing that causes many hours of hair pulling and
anguish is case sensitivity , PHP is case sensitive
(some languages are not) . Here is an example of what
I mean.
<?php
$myname = "Iain Hendry";
echo $Myname";
?>
Now we all know what we want to do , declare a variable
, assign it the value of "Iain Hendry" and
then print this on the screen but in this example we
have mis-spelt the variable name , when run the following
error is displayed on the screen.
Warning: Undefined variable: Myname in D:\testsample.php
on line 3
Example
Using your favourite HTML editor enter the following
<?php
$url = "http://www.myscripting.com";
$rank = 1;
echo "Our favourite site is ".$url;
echo "<br>";
echo "It is number ".$rank;
?>
here is the output you should get
Our favourite site is http://www.myscripting.com
It is number 1
In part 2 we will look at Data types , Type casting
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