Demonstrate Arrays in PHP

This article shows arrays in PHP, including:

• Create arrays.
• Sort arrays.
• Traverse array.
• Merge, splice, slice and dissect arrays.
• Output and test for an array.

Introduction

An array is a collection of values of the same data type. In PHP the array concept goes further in the manner that in PHP an array stores each item as a key and value pair. Keys can be numeric vales or can be associative (as a string). These numeric values determine the position of each item in the array.

Creating an Array in PHP

Numeric index example

This stores values of multiple names in each index. If the index is not provided then it will automatically increment the index for continuous value assignment as in the following:
Associative Index example

By associative index we provide a meaning to every index, like if we want to denote multiple countries by their nickname then it will be as follows:

$country=array("IND"=>"INDIA","US"=>"UNITED STATES");

Then we can access INDIA by referencing $country["IND"].

Multidimensional Array

We can create arrays of arrays, in other words multidimensional arrays. For example we can make a student's marks in various subjects as follows.
The output will be as follows:

marks = 96 grade = 1st
marks = 92 grade = 1st

Here we can reference a single item as follows:

$student["HINDI"]["marks"]

This gives the output:

96

Here basically we use either a numeric or an associative index but the key features present here is an array pointer although we actually didn’t use it.

Get array element using list()

TList has the same functionality as an array. list() provides a convenient method to assign one by one a variable value in the list extracted from an array in just one operation. This is maybe usually used when extracting data from a database of from file.

The following is an example:
The output is as follows:

A: hello; B: hey A: yes; B: hello

Explanation: Here we define a 2D array and its value is assigned one by one in the list and then we print those elements. If we simply implement it as in in the previous example.

list($a)

then it only prints:

A: hello; A: yes;

range() function for array

The range function makes a quick array filled with integer numbers. It’s syntax looks like:

range(int low, int high [,int step])

For example we want to make an array that contain 6 numbers as in the following:
That gives the following output:

1 2 3 4 5 6
1 3 5 7
A D G J M P S V Y

Output Explanation: In the preceding example for $id we just provide a range from 1 to 6 and the difference between each number is 1 by default.
For $id1 we start from 1 to 8 but there is the difference between 2 that we provided to it.

For $id2 we print the range from A to Z and the difference between each character is 3. This difference and calculation is basically done on each character ASCII value.

The range() function not always increments the ASCII, it makes a loop from the start value to the end value.

Testing for an array

Sometimes we need to verify whether the given variable is an array. Then this can be verified using the built-in function is_array(). It’s syntax looks as follows.

Boolean is_array(variable)

The preceding function returns true if the passed variable is an array else it returns false.
This gives the following output:

$states is an array: TRUE
$state is an array: FALSE

Outputting an array

The output of array's element can be done by iterating each key and this is simply accomplished by a foreach() loop. This can be as follows:
This gives the following output:

6 5 4 3 2 1

For arrays of array elements we can use the vprintf() function that allows us to easily display array contents using the same formatting syntax used by the printf() and sprintf() functions. If we want to send the output to the string, in other words store it in a string then we can use the vsprintf() function as in the following:
This produces following output:

Name: sandeep jangid
E-mail: [email protected]
Phone: 98989898

Name: sanjeev baldia
E-mail: [email protected]
Phone: 818546454

Name: rahul prajapat
E-mail: [email protected]
Phone: 212545485

The print_r() function

The print_r() function accepts a variable and sends its contents to standard output, returning TRUE on success and FALSE otherwise. It is usually used for testing an array output. It makes an array content into readable format. It’s syntax looks like this.

boolean print_r(mixed variable [, boolean return])

The following:
Produces the following output:

Array ( [IND] => INDIA [US] => UNITED STATES )

If we want only to output the array values then this can be done using the optional parameter of print_r(variable, true) function to true otherwise false.

So if we use print_r($country,true) as in our previously example then it produces the following output:

INDIA UNITED STATES

Adding or removing array element

PHP provides a number of functions to shift, pop, push, shrink an array.

Those methods are:

1. array_unshift()=adds elements to the front of the array.
2. array_push()=adds values to the end of the array and returns the total count of the array element.
3. array_shift()=removes and returns the first item found in an array.
4. array_pop()=removes and returns the last element from an array.

Note: In all the preceding array functions, after performing any add and remove operation, the index values of the array will be modified depending on their respective function but associative keys never get a change.

Let’s see, the following:

Gives the following output:

user1 user2 user3 user4 user5

Locating array element

Searching an array element: The in_array() function searches an array for a specific value, returning TRUE if the value is found and FALSE if fails to be found. Its syntax is as follows.

boolean in_array(string to be found, in which array want to found [, boolean strict])

Here the third parameter strict is to make our searching type specific or not.

Consider the following example:
That gives the following output:

Element not found

Searching associative array keys

This uses the array_key_exists() function to find a specific key in an associative array. For example:
This gives the following output:

elemant found

Searching associative array values

This uses the array_key_exists() function to find a specific value in an associative array and returns it’s key. For example:
This gives the following output:

user1

Retrieving array keys

The array_keys() function returns an array consisting of all keys located in an array. Its prototype follows.

array array_keys(array variable [, search_value to be specific search [, boolean preserve_keys]])

Here search_value if included then only the keys that will be matched are shown. Setting the optional preserve_keys parameter to true will cause the array value's keys to be preserved in the returned array. The following:
Produces the following output:

Array ( [0] => user1 [1] => user2 [2] => user3 [3] => user4 )

Retrieving array values: The array_values() function returns an array consisting of all keys located in an array. The following:
Produces the following output:

Array ( [0] => sandeep [1] => pankaj [2] => rahul [3] => neeraj )

Traversing Array

Get current array key

To get the current array key we use the key() function to provide the first index value and in the following example we use next() to increment the key.

The following:
Produces the output as follows:

user1
user2
user3
user4

Get current array value

To get the current array key we use the current() function to give us the first index value and in the following example we use next() to increment the key.

The following:
Produces the following: output:

sandeep
pankaj
rahul
neeraj

Get current array’s key value pair

To get an array’s current key value pair we can use the each() function that takes an array name as argument and automatically increments to the next key after retrieving the first key value pair. If the pointer is residing at the end of the array before executing each(), FALSE is returned.

The following: