What is an array in php?
An Array is a collection of data values. It can also define as a collection of key/value pairs. An array can store multiple values in as a single variable. because array store values under a single variable name. Each array element has index which is used to access the array element. An array can also store diffrent type of data values. That means you can store integer and string values in the same array. PHP has lot of array functions to deal with arrays. You can store integers, strings, floats or objects in arrays. Arrays are very important in any programming language. You can get complete idea of arrays by reading this tutorial.
How to define an array in PHP?
$numbers =
array(1,2,3,4,5,6,7,8,9,0);
This will create an array of 10 elements. array is the pHP keyword that use to define a array. Not like other programming languages array size is not a fixed value. You can expand it at any time. That means you can store any value in the array you create. PHP will ready to adjust the size of the array.
Why arrays are important?
- Store similar data in a structured manner.
- Easy to access and change values.
- You can define any number of values (No need to define multiple variables).
- Save time and resources.
- To store temporary data.
In PHP there are two types of arrays.
- Numeric/Indexed Arrays
- Associative Arrays
Numeric Arrays
An indexed or a numeric array stores its all elements using numerical indexes. Normally indexed array begins with 0 index. When adding elements to the array index will be automatically increased by one. So always maximum index may be less than one to the size of the array. Following example shows you how to declare numeric arrays in pHP
e.g.
$programming_languages =
array(,,);
Also you can define indexed/numeric arrays as follows.
$programming_languages[0]=;
$programming_languages[1]=;
$programming_languages[2]=;
Actually you don't need to specify the index, it will be automatically created. So you can also define it as bellow.
$programming_languages[]=;
$programming_languages[]=;
$programming_languages[]=;
Above array has three elements. The value 'PHP' has the index of 0 while 'C#' has index of 2. You can add new elements to this array. Then index will be increased one by one. That means the next element index will be 3. You can use that integer index to access array index as follows
echo $programming_languages[2];
or
echo $programming_languages{2};
If you access an element which is not exists in the numeric array you will get an error message like
Notice: Undefined offset: 4 in D:\Projects\array.php on line 7.
Associative Arrays
Associative arrays have keys and values. It is similar to two-column table. In associative arrays, key is use to access the its value. Every key in an associative array unique to that array. That means you can't have more than one value with the same key. Associative array is human readable than the indexed arrays. Because you can define a key for the specific element. You can use single or double quotes to define the array key. Following example explains you how to declare associative arrays in pHP
Method 1:
$user_info =
array(
'name'=>,
'age'=>,
'gender'=>,
'status'=>);
Method 2:
$user_info[
'name']=;
$user_info[
'age']=;
$user_info[
'gender']=;
$user_info[
'status']=;
Above array has four key pair values. That means array has 4 elements. Each element has a specific key. We use that key to access array element in associative arrays. You can't duplicate the array key. If there a duplicate key, the last element will be used.
echo $user_info[
'name'];
or
echo $user_info{
'name'};
If you access an element which is not exists in the associative array you will get an error message like
Notice: Undefined index: country in D:\Projects\array.php on line 11.
Multidimensional Arrays
Multidimensional arrays are arrays of arrays. That means one element of the array contains another array. Like wise you can define very complex arrays in pHP Suppose you have to store marks of the students according to their subjects in a class room using an array, You can use a multidimensional array to perform the task. See bellow example.
Syntax:
$marks=
array(
'nimal'=>
array(
'English'=>67,
'Science'=>80,
'Maths'=>70),
'sanka'=>
array(
'English'=>74,
'Science'=>56,
'Maths'=>60),
'dinesh'=>
array(
'English'=>46,
'Science'=>65,
'Maths'=>52)
);
echo $marks[
'sanka'][
'English'];
You can use
array_keys() method to get all keys of an array. This will returns an array of keys.
print_r(
array_keys(
$marks));
//This will output Array ( [0] => nimal [1] => sanka [2] => dinesh )
Note: you can use student number and subject number
instead of using student name and subject name.
2. How to get the size of an array using pHP?
Sometimes you may need to get how many elements exists in the array or the size of the array. You can use pHP in-built methods to find the size of a any array. See bellow examples. Also you can count all elements in a multidimensional array using count() function.
<?pHP
$countries = array();
echo count($countries); echo '<br/>';
echo sizeof($countries);
$exchange_rates=array(
=>array(),
=>array(),
=>array()
);
echo count($exchange_rates,true);
echo count($exchange_rates,COUNT_RECURSIVE);
echo count($exchange_rates,COUNT_NORMAL);
?>
