PHP

PHP Variables

 

 

A variable is just a storage area. You put things into your storage areas (variables)
so that you can use and manipulate them in your programmes. Things you’ll want
to store are numbers and text.

If you’re ok with the idea of variables, then you can move on. If not, think
of them like this. Suppose you want to catalogue your clothing collection. You
enlist two people to help you, a man and a woman. These two people are going
to be your storage areas. They are going to hold things for you, while you tally
up what you own. The man and the woman, then, are variables.

You count how many coats you have, and then give these to the man. You count
how many shoes you have, and give these to the woman. Unfortunately, you have
a bad memory. The question is, which one of your people (variables) holds the
coats and which one holds the shoes? To help you remember, you can give your
people names! You could call them something like this:

mr_coats
mrs_shoes

But it’s entirely up to you what names you give your people (variables). If
you like, they could be called this:

man_coats
woman_shoes

Or

HimCoats
HerShoes

But because your memory is bad, it’s best to give them names that help you
remember what it is they are holding for you. (There are some things your people
balk at being called. You can’t begin their names with an underscore (_), or
a number. But most other characters are fine.)

OK, so your people (variables) now have name. But it’s no good just giving
them a name. They are going to be doing some work for you, so you need to tell
them what they will be doing. The man is going to be holding the coats. But
we can specify how many coats he will be holding. If you have ten coats to give
him, then you do the “telling” like this:

mr_coats = 10

So, the variable name comes first, then an equals sign. After the equals sign,
you tell your variable what it will be doing. Holding the number 10, in our
case. (The equals sign, by the way, is not really an equals sign. It’s called
an assignment operator. But don’t worry about it, at this stage. Just remember
that you need the equals sign to store things in your variables.)

However, you’re learning PHP, so there’s something missing. Two things, actually.
First, your people (variables) need a dollar sign at the beginning (people are
like that). So it would be this:

$mr_coats = 10

If you miss the dollar sign out, then your people will refuse to work! But
the other thing missing is something really picky and fussy – a semi-colon.
Lines of code in PHP need a semi-colon at the end:

$mr_coats = 10;

If you get any parse errors when you try to run your code, the first thing
to check is if you’ve missed the semi-colon off the end. It’s very easy to do,
and can be frustrating. The next thing to check is if you’ve missed out a dollar
sign. But back to our people (variables).

So the man is holding ten coats. We can do the same thing with the other person
(variable):

$mrs_shoes = 25;

So, $mrs_shoes is holding a value of 25. If we then wanted to add up how many
items of clothes we have so far, we could set up a new variable (Note the dollar
sign at the begining of the new variable):

$total_clothes

We can then add up the coats and the shoes. You add up in PHP like this:

$total_clothes = $mr_coats + $mrs_shoes;

Remember, $mr_coats is holding a value of 10, and $mrs_shoes is holding a value
of 25. If you use a plus sign, PHP thinks you want to add up. So it will work
out the total for you. The answer will then get stored in our new variable,
the one we’ve called $total_clothes. You can also add up like this:

$total_clothes = 10 + 35;

Again, PHP will see the plus sign and add the two together for you. Of course,
you can add up more than two items:

$total_clothes = 10 + 35 + 7 + 38 + 1250;

But the idea is the same – PHP will see plus signs and then add things up.
The answer is then stored in your variable name, the one to the left of the
equals sign.

 

In the next part, we’ll take a look at how to put text into variables.

Kaynak : https://www.homeandlearn.co.uk/php/php2p1.html ‘sitesinden alıntı

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