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Arrays and PHP: A Primer


For many years, arrays have been used to logically store and sequence data. They have also been the point of confusion for many developers. In this article, Tuna will talk about the structure of arrays and how you can create and manipulate arrays with the PHP scripting language.

Author Info:
By: Tuna Celik
Rating: 4 stars4 stars4 stars4 stars4 stars / 30
December 20, 2001
TABLE OF CONTENTS:
  1. · Arrays and PHP: A Primer
  2. · The fundamentals of memory allocation
  3. · Arrays and their uses
  4. · Single dimension arrays
  5. · Multi-dimensional arrays
  6. · Conclusion

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Arrays and PHP: A Primer - Arrays and their uses
(Page 3 of 6 )

Before we continue, you should understand that an array is simply a value stored in memory with more than one segment of allocation, meaning that one variable can "store" more than one value. Each value is indexed either numerically, or by a text reference. Here's an example:

<?

$Arthur[0] = "Value01";

$Arthur[1] = "Value02";

$Arthur[2] = "Value03";

$Arthur[3] = "Value04";

$Arthur[4] = "Value05";

?>


As you can see from the example above, the $Arthur variable is now an array, and can take five values, which are indexed from 0 to 4. Here's an idea of how the $Arthur variable would look in memory:

The $Arthur array in memory

The address of the $Arthur variable is the address of the first index, 0. The address of each index after that is calculated as the address of the previous index, plus the size of the data type being stored. For example, if $Arthur[0] has the address of 0x19DA00 and the $Arthur array was storing only integers (4 bytes), then the address of $Arthur[1] would be 0x19DA04.

To print out the values stored in the $Arthur array, we would use this snippet of code:

<?

$arthur[0] = "Get Value 01";

$arthur[1] = "Get Value 02";

$arthur[2] = "Get Value 03";

$arthur[3] = "Get Value 04";

$arthur[4] = "Get Value 05";

for($i = 0; $i < 5; $i++) {

print $arthur[$i] . "<br>";

}

?>


The print command will output each of the values to our browser, as shown below:

The results of printing each index in the $Arthur array

There are many different ways that we can declare both single and multi-dimensional arrays in PHP. Let's look at some of them now.
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