The following table shows some of the more common array manipulation functions.

Creating an array and initialize it with the same values

The PHP array_pad () function allows you to create an array with values initialized to the same content. The array_pad () function takes three arguments. The first arguments are the array itself, the next arguments are a number indicating the padding size, and the last argument is the value that will be used to pad or initialize the array content.

The array_pad () function doesn’t modify the original array during the padding process. If you want to have the padded result back to the original array, you have to assign the result of the array_pad () function to the original array.

Another thing that you need to know is that if you give the second argument to the array_pad function a positive value, the pad will be added at the end of the array. But if you give a negative value for the second argument, the array will be padded at the start of the array.

Let’s take a look at some code snippet below:

<?php
//
// Creates an array with 5 elements and initialize each element
// with 0
//
$numbers = array_pad(array(), 5, 0);
echo "Numbers: ";
print_r(implode(', ', $numbers));
echo "\n";

//
// First we create a vowels array with some values. Next we create
// another array by padding the vowels array to make it to be 10 in
// length and pad it with an empty string.
//
$vowels = array('a', 'i', 'u', 'e', 'o');
$padded = array_pad($vowels, 10, '');
echo "Vowels : ";
print_r(implode(', ', $padded));
echo "\n";

//
// Assign the value back the the $vowel original array.
//
$vowels = array_pad($vowels, 10, '');
echo "Vowels : ";
print_r(implode(', ', $vowels));
echo "\n";

//
// Using a negative value to add padding at the start of the array.
//
$random = array(3, 5, 1, 2, 9);
$randomPadded = array_pad($random, -10, 0);
echo "Numbers: ";
print_r(implode(', ', $randomPadded));

?>  

And here is the result of the code snippet:

Numbers: 0, 0, 0, 0, 0
Vowels : a, i, u, e, o, , , , ,
Vowels : a, i, u, e, o, , , , ,
Numbers: 0, 0, 0, 0, 0, 3, 5, 1, 2, 9

Creating an array with a range of values

In this code snippet example, you will learn how to create an array and assign a range of values to the array. To do this in PHP, you can use the range () function. The range () function creates an array of consecutive integer or character values between the two values passed as the arguments to this function.

Here is the code snippet:

<?php
//
// Creates a range of integers from 1 to 10
//
$numbers = range(1, 10);
echo "Numbers: ";
print_r(implode(', ', $numbers));
echo "\n";

//
// Creates a lowercase characters sequence from a to z
//
$lowercaseChars = range('a', 'z');
echo "Lowercase: ";
print_r(implode(', ', $lowercaseChars));
echo "\n";

//
// Creates a uppercase characters sequence from A to Z
//
$uppercaseChars = range('A', 'Z');
echo "Uppercase: ";
print_r(implode(', ', $uppercaseChars));
echo "\n";

//
// Creates a range of reversed integers from 10 to 1
//
$reverseNumbers = range(10, 1);
echo "Reverse Numbers: ";
print_r(implode(', ', $reverseNumbers));
echo "\n";  

Executing this code snippet will give you the following result:

Numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Lowercase: a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z
Uppercase: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z
Reverse Numbers: 10, 9, 8, 7, 6, 5, 4, 3, 2, 1

Removing some elements from array

To remove some elements from an array, we can use the array_splice () function. This function will take arguments such as the input array, the offset and the length. This function will return the extracted elements from the input array. And the input array will be modified to not contain the removed elements.

There are some rules to remember regarding the offset and the length parameter.

• When the offset is defined and has a positive value, it will start from the beginning of the array.

• When the offset has a negative value, it will start from the end of the array.

• When the length is defined and has a positive value, it will have that many elements in the sequence.

• When the length has a negative value, it will stop many elements from the end of the array.

Let’s see the code snippet below:

<?php
$fruits = array('orange', 'apple', 'banana', 'mango', 'grape', 'lemon');
//
// Remove banana, mango, grape and lemon from the $fruits.
//
$result = array_splice($fruits, 2);
print 'Fruits: ' . implode(', ', $fruits) . "\n";
print 'Result: ' . implode(', ', $result) . "\n";

$fruits = array('orange', 'apple', 'banana', 'mango', 'grape', 'lemon');
//
// Remove banana and mango the $fruits.
//
$result = array_splice($fruits, 2, 2);
print 'Fruits: ' . implode(', ', $fruits) . "\n";
print 'Result: ' . implode(', ', $result) . "\n";

$fruits = array('orange', 'apple', 'banana', 'mango', 'grape', 'lemon');
//
// Remove apple, banana, mango and grape from the $fruits.
//
$result = array_splice($fruits, 1, -1);
print 'Fruits: ' . implode(', ', $fruits) . "\n";
print 'Result: ' . implode(', ', $result) . "\n"; 

The result of the snippet:

Fruits: orange, apple
Result: banana, mango, grape, lemon

Fruits: orange, apple, grape, lemon
Result: banana, mango

Fruits: orange, lemon
Result: apple, banana, mango, grape

Eliminate duplicate elements in array

You want to eliminate duplicate elements from an array to create an array with a unique value. To do this, you can use the array_unique() function. This function takes in the array as an argument and will return you a new array with unique elements in it. Let see the snippet below:

<?php
// The $color array that contains duplicate elements.
$colors = array(
'red', 'green', 'blue', 'yellow', 'red', 'green', 'yellow'
);

// Eliminates the duplicate elements from the $colors array.
$uniqueColors = array_unique($colors);

print_r($uniqueColors);  

Printing out the contents of an array variable

<?php
$myArray = array('a', 'b', 'c', 'd', 'e');

// Print out using for loop.
for ($i = 0; $i < count($myArray); $i++) {
echo $myArray[$i];
}

echo "\n";

// Print out using foreach loop.
foreach (array_keys($myArray) as $key) {
echo $myArray[$key];
}

echo "\n";

// Print out using while loop.
$index = 0;
while ($index < count($myArray)) {
echo $myArray[$index];
$index++;
}

echo "\n";

// Print out using implode(), convert array into string
// separated each element using comma.
$str = implode(', ', $myArray);
echo $str;  

<?php
//
// Creates array and print it.
//
$numbers = array(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
print_r($numbers);

//
// Pick single key of an array randomly.
//
$key = array_rand($numbers);
echo "arrayKey = $key\n";

$key = array_rand($numbers);
echo "arrayKey = $key\n";

$key = array_rand($numbers);
echo "arrayKey = $key\n";

//
// Pick multiple keys of an array randomly.
//
$keys = array_rand($numbers, 3);
print_r($keys);  

 <?php
$array = array(
"color" => "blue",
"size" => 8.5,
"price" => 100
);

//
// Finds whether $array is an array.
//
if (is_array($array)) {
echo "\$array is an array.";
} else {
echo "\$array is not an array.";
}  

<?php
$array = array (
"one" => 1,
"two" => 2,
"three" => 3,
"four" => 4,
"student" => array("name" => "Alice", "age" => 15)
);

//
// Print keys for of the array.
//
$keys = array_keys($array);
print_r($keys);

//
// Get the value from the array using the keys
//
echo "Print array contents:\n";
for ($i = 0; $i < count($keys); $i++) {
if (is_array($array[$keys[$i]])) {
print_r($array[$keys[$i]]);
} else {
echo $keys[$i] . " = > " . $array[$keys[$i]] . "\n";
}
}   

Reversing elements of an array

 <?php
//
// An array of letters
//
$letters = array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j");

//
// Reverse the order of the array elements.
//
$reverse = array_reverse($letters);

echo "Original: " . implode(",", $letters) . "\n";
echo "Reverse : " . implode(",", $reverse);