PHP Arrays

In this tutorial we learn about the PHP Arrays. An array is a special variable, which can hold more than one value at a time. An array is a data structure that stores one or more similar type of values in a single value. For example if you want to store 100 numbers then instead of defining 100 variables its easy to define an array of 100 length.

Create PHP Arraya

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In PHP, the array() function is used to create an array:

array();

There are three different kind of arrays.

• Numeric array − An array with a numeric index. Values are stored and accessed in linear fashion.
• Associative array − An array with strings as index. This stores element values in association with key values rather than in a strict linear index order.
• Multidimensional array − An array containing one or more arrays and values are accessed using multiple indices

Numeric PHP Arrays

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Numeric arrays use number as access keys.

An access key is a reference to a memory slot in an array variable.

The access key is used whenever we want to read or assign a new value an array element.

Example

Following is the example showing how to create and access numeric arrays.

Here we have used array() function to create array. This function is explained in function reference.

 <?php
         /* First method to create array. */
         $numbers = array( 1, 2, 3, 4, 5);
         
         foreach( $numbers as $value ) {
            echo "Value is $value <br />";
         }
         
         /* Second method to create array. */
         $numbers[0] = "one";
         $numbers[1] = "two";
         $numbers[2] = "three";
         $numbers[3] = "four";
         $numbers[4] = "five";
         
         foreach( $numbers as $value ) {
            echo "Value is $value <br />";
         }
      ?>

This will produce the following Output:

Value is 1 
Value is 2 
Value is 3 
Value is 4 
Value is 5 
Value is one 
Value is two 
Value is three 
Value is four 
Value is five

Associative PHP Array

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Associative array differ from numeric array in the sense that associative arrays use descriptive names for id keys.

The associative arrays are very similar to numeric arrays in term of functionality but they are different in terms of their index. Associative array will have their index as string so that you can establish a strong association between key and values.

Below is the syntax for creating associative array in php.

<?php
$variable_name['key_name'] = value;

$variable_name = array('keyname' => value);
?>

HERE,

• “$variable_name…” is the name of the variable
• “[‘key_name’]” is the access index number of the element
• “value” is the value assigned to the array element.

Let’s suppose that we have a group of persons, and we want to assign the gender of each person against their names.

We can use an associative array to do that.The code below helps us to do that.

<?php
$persons = array("Mary" => "Female", "John" => "Male", "Mirriam" => "Female");
print_r($persons); 
echo ""; 
echo "Mary is a " . $persons["Mary"];
?>

Output

Array ( [Mary] => Female [John] => Male [Mirriam] => Female ) Mary is a Female

Associative array are also very useful when retrieving data from the database.

Multidimensional PHP Arrays

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A multi-dimensional array each element in the main array can also be an array. And each element in the sub-array can be an array, and so on. Values in the multi-dimensional array are accessed using multiple index.

Example

In this example we create a two dimensional array to store marks of three students in three subjects −

Example of an associative array.

<?php
         $marks = array( 
            "mohammad" => array (
               "physics" => 35,
               "maths" => 30,	
               "chemistry" => 39
            ),
            
            "qadir" => array (
               "physics" => 30,
               "maths" => 32,
               "chemistry" => 29
            ),
            
            "zara" => array (
               "physics" => 31,
               "maths" => 22,
               "chemistry" => 39
            )
         );
         
         /* Accessing multi-dimensional array values */
         echo "Marks for mohammad in physics : " ;
         echo $marks['mohammad']['physics'] . "<br />"; 
         
         echo "Marks for qadir in maths : ";
         echo $marks['qadir']['maths'] . "<br />"; 
         
         echo "Marks for zara in chemistry : " ;
         echo $marks['zara']['chemistry'] . "<br />"; 
      ?>

Output:

Marks for mohammad in physics : 35
Marks for qadir in maths : 32
Marks for zara in chemistry : 39

Why use arrays?

• Arrays easily help group related information such as server login details together
• Arrays help write cleaner code.

Summary

• Arrays are special variables with the capacity to store multi values.
• Numeric arrays use numbers for the array keys
• PHP Associative array use descriptive names for array keys
• Multidimensional arrays contain other arrays inside them.