This document provides information on working with arrays in PHP. It discusses the different types of arrays (indexed and associative), how to access and store data in arrays, add and remove values, traverse arrays using foreach loops, and several useful array functions like count(), range(), list(), array_slice(), array_merge(), array_sum(), array_unique(), array_flip(), and extract().

1. WORKING WITH ARRAYS

2. ARRYAS
• Array is a data structure, which provides the
facility to store a collection of data of same
type under single variable name.
• An array is a collection of data values,
organized as an ordered collection of key-
value pairs.

3. INDEXED VERSUS ASSOCIATIVE ARRAYS
• There are two kinds of arrays in PHP:
• indexed and associative.
• The keys of an indexed array are integers,
beginning at 0.
• Indexed arrays are used when you identify things
by their position.
• Associative arrays have strings as keys and behave
more like two-column tables.
• The first column is the key, which is used to access
the value.

4. INDEXED VERSUS ASSOCIATIVE ARRAYS
• In both cases, the keys are unique--that is, you
can't have two elements with the same key,
regardless of whether the key is a string or an
integer.
• PHP arrays have an internal order to their
elements that is independent of the keys and
values, and there are functions that you can use to
traverse the arrays based on this internal order.
• The order is normally that in which values were
inserted into the array.

5. IDENTIFYING ELEMENTS OF AN ARRAY
• You can access specific values from an array using the array
variable's name,
• followed by the element's key (sometimes called the index)
within square brackets:
• $age['Fred']
• $shows[2]
• The key can be either a string or an integer.
• String values that are equivalent to integer numbers (without
leading zeros) are treated as integers.
• Thus, $array[3] and $array['3'] reference the same element,
but $array['03'] references a different element.

6. IDENTIFYING ELEMENTS OF AN ARRAY
• You don't have to quote single-word strings.
• For instance,
• $age['Fred'] is the same as $age[Fred].
• However, it's considered good PHP style to
always use quotes, because quoteless keys
are indistinguishable from constants.

7. STORING DATA IN ARRAYS
• Storing a value in an array will create the array if it didn't
already exist.
• For example:
• echo $addresses[0]; // prints nothing
• echo $addresses; // prints nothing
• $addresses[0] = 'spam@cyberpromo.net';
• echo $addresses; // prints "Array"
• $addresses[0] = 'spam@cyberpromo.net';
• $addresses[1] = 'abuse@example.com';
• $addresses[2] = 'root@example.com';

8. STORING DATA IN ARRAYS
• $price[ 'Gasket‘ ] = 15.29;
• $price[ 'Wheel‘ ] = 75.25;
• $price[ 'Tire‘ ] = 50.00;
• An easier way to initialize an array is to use the
array( ) construct, which builds an array from its
arguments:
• $addresses = array( 'spam@cyberpromo.net',
'abuse@example.com', 'root@example.com‘ );

9. STORING DATA IN ARRAYS
• To create an associative array with array( ),
• use the => symbol to separate indexes from values:
• $price = array( 'Gasket' => 15.29,
• 'Wheel' => 75.25,
• 'Tire' => 50.00);
• $price = array(
'Gasket'=>15.29,'Wheel'=>75.25,'Tire'=>50.00);
• To construct an empty array, pass no arguments to
array( ):
• $addresses = array( );

10. STORING DATA IN ARRAYS
• You can specify an initial key with => and then a list of values.
• The values are inserted into the array starting with that key,
with subsequent values having sequential keys:
• $days = array(1 => 'Monday', 'Tuesday', 'Wednesday',
• 'Thursday', 'Friday', 'Saturday', 'Sunday');
• // 2 is Tuesday, 3 is Wednesday, etc.
• If the initial index is a non-numeric string, subsequent indexes
are integers beginning at 0.
• $whoops = array('Friday' => 'Black', 'Brown', 'Green');
• // same as
• $whoops = array('Friday' => 'Black', 0 => 'Brown', 1 =>
'Green');

11. ADDING VALUES TO THE END OF AN ARRAY
• To insert more values into the end of an existing indexed
array, use the [] syntax:
• $family = array('Fred', 'Wilma');
• $family[] = 'Pebbles'; // $family[2] is 'Pebbles'
• This construct assumes the array's indexes are numbers and
assigns elements into the next available numeric index,
starting from 0.
• Attempting to append to an associative array is almost always
a programmer mistake, but PHP will give the new elements
numeric indexes without issuing a warning:
• $person = array('name' => 'Fred');
• $person[] = 'Wilma'; // $person[0] is now 'Wilma'

12. VIEWING ARRAYS
• You can see the structure and values of any array by
using one of two functions — var_dump or print_r.
• The print_r() statement, however, gives somewhat
less information.
• To display the $customers array, use the following
functions: print_r($customers);
• To get more information, use the following
functions: var_dump($customers);

13. MODIFYING ARRAY & STORING ONE ARRAY IN ANOTHER
• Arrays can be changed at any time in the script, just as
variables can.
• The individual values can be changed, elements can be added
or removed, and elements can be rearranged.
• $customers[2] = “John”;
• $customers[4] = “Hidaya”;
• $customers[] = “Dell”;
• You can also copy an entire existing array into a new array
with this statement:
• $customerCopy = $customers;

14. REMOVING VALUES FROM ARRAYS
• Sometimes you need to completely remove a value from an
array.
• $colors = array ( “red”, “green”, “blue”, “pink”, “yellow”
);
• $colors[ 3 ] = “”;
• Although this statement sets $colors[3] to blank, it does not
remove it from the array. You still have an array with five
values, one of the values being an empty string.
• To totally remove the item from the array, you need to unset
it.
• unset($colors[3]);

15. REMOVING VALUES FROM ARRAYS
• Removing all the values doesn’t remove the
array itself
• To remove the array itself, you can use the
following statement
• unset($colors);

16. USING ARRAYS IN STATEMENTS
• Arrays can be used in statements in the same
way that variables are used in.
• You can retrieve any individual value in an
array by accessing it directly, as in the
following example:
• $Sindhcapital = $capitals[‘Sindh’];
• echo $Sindhcapital;
• You can echo an array value like this:
• echo $capitals[‘Sindh’];

17. GETTING THE SIZE OF AN ARRAY
• The count( ) and sizeof( ) functions are identical in use and
effect.
• They return the number of elements in the array.
• Here's an example:
• $family = array('Fred', 'Wilma', 'Pebbles');
• $size = count($family); // $size is 3
• These functions do not consult any numeric indexes that
might be present:
• $confusion = array( 10 => 'ten', 11 => 'eleven', 12 => 'twelve');
• $size = count($confusion); // $size is 3

18. WALKING THROUGH AN ARRAY
• Walking through each and every element in an array, in order,
is called iteration.
• It is also sometimes called traversing.
• Two ways to walk through an array:
• Traversing an array manually:
– Uses a pointer to move from one array value to another.
• Using foreach:
– Automatically walks through the array, from beginning to
end, one value at a time.

19. USING FOREACH TO WALK THROUGH AN ARRAY
• You can use foreach to walk through an array one value at a
time and execute a block of statements by using each value in
the array.
• The general format is as follows:
foreach ( $arrayname as $keyname => $valuename )
{
block of statements;
}

20. RANGE()
• You can also create an array with a range of values by using
the following function.
$years = range(2001, 2010,[step]);
• Here step is a positive number which has default value 1. Step
is used for number of increment.

21. LIST()
• You can retrieve several values at once from an array with the
list function.
• The list function copies values from an array into variables.
•
$colors=array(“red”,”green”);
list($red,$green)=$colors;

22. ARRAY_SLICE()
• You can split an array by creating a new array that contains a
subset of an existing array.
• Works same as substr works for string.
• You can do this by using following function:
$subArray = array_slice($arrayname,start,length);

23. ARRAY_MERGE()
• Conversely, you can merge two or more arrays together by
using the following function:
$bigArray = array_merge($array1,$array2,...);

24. ARRAY_SUM()
• To add all the values in an array, use the following function:
• $sum = array_sum($array);
• Of course, you are only going to add elements in an array of
numbers.
• PHP converts strings to 0 if you try to add them.

25. ARRAY_UNIQUE()
• Removes duplicate items from an array:
$names2 = array_unique($names);

26. ARRAY_FLIP()
• To swap the keys and values, use the following function:
$arrayFlipped = array_flip($testarray);

27. extract()
• Extracts array, forms variables with the names of keys or
indexes of array.
• extract($array);

28. ASSIGMENTS
1. Make a linear Search using array.
2. Take an unsorted array and sort it using bubble sort
technique.
3. Make an array which should contain intersected values of
two given arrays.