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When i first started learning PHP arrays confused me. I learned Perl
first; arrays and variables in Perl are represented with different
symbols. Not so in PHP, an array looks exactly the same as a variable, it
starts with the dollar ($) sign.
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$array =
array('cat',
'dog',
'fish',
'rabbit'); |
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Think of an array as a variable that can store many separate values. We
can access each item in the array.
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echo
$array[0];
//returns
"cat"
echo
$array[1];
//returns
"dog"
echo
$array[2];
//returns
"fish"
echo
$array[3];
//returns
"rabbit" |
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Now each item of the array
is accessed using the
variable name, followed
directly by square brackets
containing the number of the
item to be accessed. The
number listing of the array
starts at zero, so the first
item is 0, second is 1,
third is 2, etc.
Association
Let's have a look a little deeper into arrays. Arrays have a "key" and
a "value". The key is what you use to access the value.
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echo
$array[1];
// returns
"dog" |
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$array[KEY] returns the
VALUE. 0 is the key, and
"dog" is the value.
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$array =
array(0 =>
'cat', 1 =>
'dog', 2 =>
'fish', 3 =>
'rabbit', ); |
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See how each number(key) has
an association with it's
value? The "keys" don't have
to be numbers. If the keys
aren't defined, they will
default to integers to
represent each array item.
Let's define another array.
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$array =
array('name'
=> 'Jester',
'lives' =>
'England',
'occupation'
=> 'bum',
'fave_food'
=> 'pie'); |
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Now we can use the key
associated with it's value
to return the values:
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echo $array['name'];
// returns
"Jester"
echo $array['lives'];
// returns
"England"
echo $array['occupation'];
// returns
"bum"
echo $array['fave_food'];
// returns
"pie" |
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This works like associative
arrays in Perl, the methods
are almost identical. Arrays
don't stop here, they can
become very complex,
epecially when we get into
multi-dimensional arrays.
Multi-dimensional Arrays
We can define more complex
arrays like so:
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$array =
array(
"names" =>
array('person1'
=> 'Jane',
'person2' =>
'John',
'person3' =>
'Fred',
'person4' =>
'Anne'),
"places" =>
array('place1'
=>
'America',
'place2' =>
'England',
'place3' =>
'Australia',
'place4' =>
'South
Africa'),
"jobs" =>
array('job1'
=>
'accountant',
'job2' =>
'engineer',
'job3' =>
'web
designer',
'job4' =>
'secretary')
); |
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The above is a
two-dimensional array, it
has two "levels" to it. It
has three arrays stored
within one array. You can
access each array within the
array by using the KEY
associated with a deeper
array. You can then use the
keys within the deeper
arrays to access the array
values.
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echo $array['names']['person1'];
// returns
Jane.
echo $array['names']['person3'];
// returns
Fred.
echo $array['places']['place1'];
// returns
America.
echo $array['places']['place3'];
// returns
Australia.
echo $array['jobs']['job1'];
// returns
accountant.
echo $array['jobs']['job3'];
// returns
web
designer. |
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As you can see, arrays can
become very complex, you
could define three, four,
five-dimensional arrays.
Environment Variables
In PHP there are certain
environment variables
available to you in your
scripts:
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$HTTP_SERVER_VARS['REMOTE_ADDR'];
// remote IP
$HTTP_SERVER_VARS['HTTP_USER_AGENT'];
// users
user-agent
string
$HTTP_SERVER_VARS['REMOTE_HOST'];
// remote
host |
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Now that you know how arrays
work, you can use these
environment variables more
effectively. |
