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PHP : Function Reference : Array Functions : array

array

Create an array (PHP 4, PHP 5)
array array ( [mixed ...] )

Example 292. array() example

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<?php
$fruits = array (
   "fruits"  => array("a" => "orange", "b" => "banana", "c" => "apple"),
   "numbers" => array(1, 2, 3, 4, 5, 6),
   "holes"   => array("first", 5 => "second", "third")
);
?>

Example 293. Automatic index with array()

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<?php
$array = array(1, 1, 1, 1,  1, 8 => 1,  4 => 1, 19, 3 => 13);
print_r($array);
?>

The above example will output:

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Array
(
   [0] => 1
   [1] => 1
   [2] => 1
   [3] => 13
   [4] => 1
   [8] => 1
   [9] => 19
) ?>

Example 294. 1-based index with array()

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<?php
$firstquarter = array(1 => 'January', 'February', 'March');
print_r($firstquarter);
?>

The above example will output:

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Array
(
   [1] => January
   [2] => February
   [3] => March
)

Example 295. Accessing an array inside double quotes

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<?php

$foo = array('bar' => 'baz');
echo "Hello {$foo['bar']}!"; // Hello baz!

?>

Related Examples ( Source code ) » array

Examples ( Source code ) » Login ID Options
Examples ( Source code ) » Login form with Error Messages and Preserving User Input
Examples ( Source code ) » Hard code login Form
Examples ( Source code ) » The Table and HTMLTable Classes
Examples ( Source code ) » The Table Class
Examples ( Source code ) » Adding a New Node to contact.xml
Examples ( Source code ) » Turning an XML Document into an Array
Examples ( Source code ) » Get data from database query
Examples ( Source code ) » Connect To MySQL Database
Examples ( Source code ) » Store query result in an array
Examples ( Source code ) » Store query result in an associate array
Examples ( Source code ) » Reference columns by name
Examples ( Source code ) » Table-Creation Script
Examples ( Source code ) » Create table and install data
Examples ( Source code ) » Encoding Data

Code Examples / Notes » array

webmaster
When using an array to create a list of keys and values for a select box generator which will consist of states I found using "NULL" as an index and ""(empty value) as a value to be useful:
<?php
$states = array(
0 => 'Select a State',
NULL => '',
1 => 'AL - Alabama',
2 => 'AK - Alaska',
# And so on ...
);
$select = '<select name="state" id="state" size="1">'."\r\n";
foreach($states as $key => $value){
$select .= "\t".'<option value="'.$key.'">' . $value.'</option>'."\r\n";
}
$select .= '</select>';
echo $select;
?>
This will print out:
<select name="state" id="state" size="1">
<option value="0">Select a State</option>
<option value=""></option>
<option value="1">AL - Alabama</option>
<option value="2">AK - Alaska</option>
# And so on ...
</select>
Now a user has a blank value to select if they later decide to not provide their address in the form. The first two options will return TRUE when checked against the php function - EMPTY() after the form is submitted when processing the form

xftp
This is a small script that shows how to use an array of a Class.
<?
class test{
var $test1;
var $test2;
}
 
 
$a = array();  
$a[] = new test;
$a[0]->test1 = 1;
$a[0]->test2 = 1;
$a[1]->test1 = 2;
$a[1]->test2 = 2;
 
$x = $a[0]->test1;
$y = $a[0]->test2;
echo "$x - $y";
 
?>

phpm
This helper function creates a multi-dimensional array. For example, creating a three dimensional array measuring 10x20x30: <?php $my_array = multi_dim(10, 20, 30); ?>
<?php
function multi_dim()
{
$fill_value = null;

for ($arg_index = func_num_args() - 1; $arg_index >= 0; $arg_index--) {
$dim_size = func_get_arg($arg_index);
$fill_value = array_fill(0, $dim_size, $fill_value);
}

return $fill_value;
}
?>

php
This function converts chunks of a string in an array:
function array_str($str, $len) {
 $newstr = '';
 for($i = 0; $i < strlen($str); $i++) {
   $newstr .= substr($str, $i, $len);
 }
 return $newstr;
}
use it as:
$str = "abcdefghilmn";
echo "<table width=\"100%\">\n";
foreach(array_str($str, 4) as $chunk) {
 echo "<tr><td>".$chunk."</td></tr>\n";
}
echo "</table>";
this prints:
------
abcd
------
efgh
------
ilmn
------
It don't use regular expressions. Please add this function to php :)

jjm152
The easiest way to "list" the values of either a normal 1 list array or a multi dimensional array is to use a foreach() clause.
Example for 1 dim array:
<?php
  $arr = array( 1, 2, 3, 4, 5 );
  foreach ( $arr as $val ) {
      echo "Value: $Val\n";
     }
?>
For multi dim array:
<?php
    $arr = array( 1 => 'one', 2 => 'two', 3 => 'three', 4 => 'four, 5 => 'five');
     foreach ( $arr as $key => $value ) {
      echo "Key: $key, Value: $value\n";
     }
?>
This is quite possibly the easiest way i've found to iterate through an array.

10-may-2003 11:53
Similarly to a comment by stlawson at sbcglobal dot net on this page:
http://www.php.net/basic-syntax.instruction-separation
It is usually advisable to define your arrays like this:
$array = array(
    'foo',
    'bar',
);
Note the comma after the last element - this is perfectly legal. Moreover,
it's best to add that last comma so that when you add new elements to the
array, you don't have to worry about adding a comma after what used to be
the last element.
<?php
$array = array(
    'foo',
    'bar',
    'baz',
);
?>

james
re: m.izydorski 29-May-2005 07:17
The reason the code snippet below is "very slow" is because the backtick (`) is a shell call delimiter, not a string delimiter. Every element of the array would be executed as a shell call and the result stored as array elements.
<?
// Very slow:
$my_array = array(`sign`, `cat01`, `cat02`, ... , `cat40`,`terra01`, `terra02`, ... , `terra50`);
?>
See the backtick operator page for more information:
http://uk2.php.net/manual/en/language.operators.execution.php

slicky
Notice that you can also add arrays to other arrays with the $array[] "operator" while the dimension doesn't matter.
Here's an example:
$x[w][x] = $y[y][z];
this will give you a 4dimensional assosiative array.
$x[][] = $y[][];
this will give you a 4dimensional non assosiative array.
So let me come to the point. This get interessting for shortening things up. For instance:
<?php
foreach ($lines as $line){
if(!trim($line)) continue;
$tds[] = explode("$delimiter",$line);
}
?>

rubein
Multidimensional arrays are actually single-dimensional arrays nested inside other single-dimensional arrays.
$array[0] refers to element 0 of $array
$array[0][2] refers to element 2 of element 0 of $array.
If an array was initialized like this:
$array[0] = "foo";
$array[1][0] = "bar";
$array[1][1] = "baz";
$array[1][2] = "bam";
then:
is_array($array) = TRUE
is_array($array[0]) = FALSE
is_array($array[1]) = TRUE
count($array) = 2 (elements 0 and 1)
count($array[1] = 3 (elements 0 thru 2)
This can be really useful if you want to return a list of arrays that were stored in a file or something:
$array[0] = unserialize($somedata);
$array[1] = unserialize($someotherdata);
if $somedata["foo"] = 42 before it was serialized previously, you'd now have this:
$array[0]["foo"] = 42

michael dot bommarito
Just in case anyone else was looking for some help writing an LU decomposition function, here's a simple example.  
N.B. All arrays are assumed to begin with index 1, not 0.  This is not hard to change, but make sure you specify array(1=>...), not just array(...).
Furthermore, this function is optimized to only consider variable elements of the matrices.  As $L will be a lower triangular matrix, there is no need to compute the elements of either the diagonal or the upper triangle; likewise with $U.
This function also does not check to verify that the input matrix is non-singular.
/*
* LU Decomposition
* @param $A initial matrix (1...m x 1...n)
* @param $L lower triangular matrix, passed by reference
* @param $U upper triangular matrix, passed by reference
*/
function LUDecompose($A, &$L, &$U) {
$m = sizeof($A);
$n = sizeof($A[1]);
for ( $i = 1; $i <= $m; $i++ ) {
$U[$i][$i] = $A[$i][$i];

for ( $j = $i + 1; $j <= $m; $j++ ) {
$L[$j][$i] = $A[$j][$i] / $U[$i][$i];
$U[$i][$j] = $A[$i][$j];
}
for ( $j = $i + 1; $j <= $m; $j++ ) {
for ( $k = $i + 1; $k <= $m; $k++ ) {
$A[$j][$k] = $A[$j][$k] - ($L[$j][$i] * $U[$i][$k]);
}
}
}
return;
}

jonovic
Just a short message. There is a problem with array creating with references using function array(). Array is function as any other, so you cannot forse parameters to be passed by reference in call time! This manner is deprecated and you will go into troubles soon with you web provider's php.ini settings.
DO NOT USE!
$my_array = array(&$element_1, &$element_2);
INSTEAD USE!
$my_array[] =& $element_1;
$my_array[] =& $element_2;
This problem should be solved soon since you cannot use many array functions like array_push() etc.

craig
Just a helpful note, when creating arrays, avoid doing:
<?php
 $var[key] = "value";
?>
PHP will look for a constant called 'key' before it will treat it as a string, thus slowing down execution (I've seen files with thousands of these and PHP taking over a second to execute).
Always concider switching on E_NOTICE before releasing any PHP, it'll help avoid making simple mistakes.

markus dot elfring
It seems to me that the use of brackets with multidimensional arrays is not described here.
But the following examples work:
<?php
$value = $point['x']['y'];
$message[1][2][3] = 'Greetings';
?>

mads
In PHP 4.2.3 (and maybe earlier versions) arrays with numeric indexes may be initialized to start at a specific index and then automatically increment the index. This will save you having to write the index in front of every element for arrays that are not zero-based.
The code:
<?php
                 $a = array
(
21 => 1,
2,
3,
);
print '<pre>';
print_r($a);
print '</pre>';
?>
will print:
<?php
Array
(
   [21] => 1
   [22] => 2
   [23] => 3
)
?>

jay
If you want to create an array of a set size and you have PHP4, use
array_pad(array(), $SIZE, $INITIAL_VALUE); This can be handy if you wish
to initialize a bunch of variables at once:
list($Var1, $Var2, etc) = array_pad(array(), $NUMBER_OF_VARS,
$INITIAL_VALUE);
Jay Walker
Las Vegas Hotel Associate
http://www.ezlasvegas.net

php-manual
If you want to create an array of a set size and you have PHP4, use array_pad(array(), $SIZE, $INITIAL_VALUE); This can be handy if you wish to initialize a bunch of variables at once:
list($Var1, $Var2, etc) = array_pad(array(), $NUMBER_OF_VARS, $INITIAL_VALUE);

brian
If you need, for some reason, to create variable Multi-Dimensional Arrays, here's a quick function that will allow you to have any number of sub elements without knowing how many elements there will be ahead of time. Note that this will overwrite an existing array value of the same path.
<?php
// set_element(array path, mixed value)
function set_element(&$path, $data) {
return ($key = array_pop($path)) ? set_element($path, array($key=>$data)) : $data;
}
?>
For example:
<?php
echo "<pre>";
$path = array('base', 'category', 'subcategory', 'item');
$array = set_element($path, 'item_value');
print_r($array);
echo "</pre>";
?>
Will display:
Array
(
   [base] => Array
       (
           [category] => Array
               (
                   [subcategory] => Array
                       (
                           [item] => item_value
                       )
               )
       )
)

mike mackintosh
If you need to add an object as an array key, for example an object from Simple XML Parser, you can use the following.
File.XML
<?xml version="1.0" encoding="UTF-8"?>
<Settings type="General">
 <Setting name="SettingName">This This This</Setting>
</Settings>
The script:
<?php
$raw = $xml =  new SimpleXMLElement('File.XML');
foreach($raw->Setting as $A => $B)
{
// Set Array From XML
$Setting[(string) $B['name']] = (string)  $B[0];
}
?>
By telling the key to read the object as a string, it will let you set it.
Hope this helps someone out!

rdude
If you are creating an array with a large number of static items, you will find serious performance differences between using the array() function and the $array[] construct. For example:
<?
// Slower method
$my_array = array(1, 2, 3, … 500);

// Faster method
$my_array[] = 1;
$my_array[] = 2;
$my_array[] = 3;
…
$my_array[] = 500;
?>

christian w.
If you already created an associative array you can add a new element by:
<?php
$arr = array("foo" => 1);
print_r($arr);
$arr["bar"] = 2;
print_r($arr);
?>
Output:
Array
(
   [foo] => 1
)
Array
(
   [foo] => 1
   [bar] => 2
)

admin
I wrote the code below to load values from a query, than save them to two variables, code and text. It is used to replace values using str_replace.
The tricky part(for me) was building the two variables from a query.
//grab available classes - table of id numbers and //corresponding titles
$class_values = mysql_query($sql_classes);
// grab avaialable book conditions
$condition_values = mysql_query($sql_conditions);
// build conversion tables
// one for class one for coinditoion
   $condcode = array();
   $condtext = array();        
   $classcode = array();
   $classtext = array();
$i=0;
 while ($row=mysql_fetch_row($condition_values)){
//echo $row[0]." ".$row[1];
   $condcode[$i] =$row[0];
   $condtext[$i] =$row[1];
$i++;    
 }
$i=0;
 while ($row=mysql_fetch_row($class_values)){
//echo $row[0]." ".$row[1];
   $classcode[$i] = $row[0];
   $classtext[$i] = $row[1];    
++$i;    
 }
// there is no output, but now four arrays exist .
//there are four becuase theycame from two tables
// now i call
//example:
echo str_replace($classcode,$classtext,1);
//would output
Algebra
//

sam yong - hellclanner
I wanted to put a large range of numbers into an array but it seems to me that the array function don't have that kind of ability for me to put in a range of numbers without having to list down every single number.
Here's my solution:
<?php
function arr_range($r1,$r2){
// the end range is smaller than the start range
// switch around
if($r2 < $r1){
$t = $r1;
$r1 = $r2;
$r2 = $t;
unset($t);
}
$return_val = array();
$i = 0;
// for each value of the range
// add the value into the temparory array
for($i = $r1;$i<=$r2;$i++){
$return_val[] = $i;
}
// return the values in array form
return $return_val;
}
// example usages
$values = arr_range(100,6000);
$values = arr_range(1996,2010);
$values = arr_range(50,25); // it works
$values = arr_range(-64,1024);
?>

bill
I wanted to be able to control the flow of data in a loop instead of just building tables with it or having to write 500 select statements for single line items. This is what I came up with thanks to the help of my PHP brother in FL. Hope someone else gets some use out it.
<?
//set array variable
$results = array();
//talk to the db
$query = "SELECT * FROM yourtable";
$result = mysql_query($query) or die(mysql_error());
//count the rows and fields
$totalRows = mysql_num_rows($result);
$totalFields = mysql_num_fields($result);
//start the loop
for ( $i = 0; $i < $totalRows; ++$i ) {
//make it 2 dim in case you change your order
 $results[$i] = mysql_fetch_array($result);
//call data at will controlling the loop with the array
echo $results[your_row_id]['your_field_name']; }
//print the entire array to see what lives where
print_r($results);  ?>

marcel
i tried to find a way to create BIG multidimensional-arrays. but the notes below only show the usage of it, or the creation of small arrays like $matrix=array('birne', 'apfel', 'beere');
for an online game, i use a big array (50x80) elements.
it's no fun, to write the declaration of it in the ordinary way.
here's my solution, to create an 2d-array, filled for example with raising numbers.
<?php
$matrix=array();
$sx=30;
$sy=40;
$i=1;
for ($y=0; $y<$sy; $y++)
{
array_push($matrix,array());
for ($x=0; $x<$sx; $x++)
{
array_push($matrix[$y],array());
$matrix[$x][$y]=$i;
$i++;
}
}
?>
if there is a better way, plz send an email. i always want to learn more php!

stephen
I think I may have found a simpler, slightly more logical route to solving the previous problem. I came across this solution when retreving data from MySql which in most cases was for individual bits of data, but also needed to reference a set of sub data from a second table.
<?php
// -------------------------------------------------------
// Function: db_get_data()
// Desc: Build array of data from mysql table and sub table(s)
// PreCondition: None
// Returns: Array of rows / sub rows from db,
// -------------------------------------------------------
function db_get_data()
{
$ar_sub = array();

/* [ .... code for connecting and querying DB .... ] */
// Retireve from first table
$row = mysql_fetch_row($result);

// Get first two fields
$ar_details['item0'] = $row ['field0'];
$ar_details['item1'] = $row ['field1'];
// Using result from query on sub table
// for each sub row, 'push' data on sub array
while($row_sub = mysql_fetch_array($result_sub))
{
array_push($ar_sub, $row_sub['sub_field']);
}
// Add sub array as element of parent array
$ar_details['item3'] = $ar_sub;
return $ar_details;
}
// -------------------------------------------------------
// Retrieving array data
// -------------------------------------------------------
// Call function
$arr_details = db_get_data()
// Output Data
echo $ar_details['item1'];
echo $ar_details['item2'];
// For each record in sub array....
for($i=0; $i<count($ar_details['item3']); $i++)
{
echo $ar_details['item3'][$i];
}
?>
For extra sub tables the process can be repeated by adding more sub arrays, and each sub array can hold as much data as you like. Therefore allowing you to build an ever expanding tree as required. If you have the option I would recommend using nested classes though :)

deepak_pradhan
I have seen that most of the time we get confused with Mult-Dimensional arrays.
I found print_r to be very helpful here.
Say the defined array is:
$a = array(1,2,array("A","B"));
print_r ($a);
Should give result like this:
Array ( [0] => 1 [1] => 2 [2] => Array ( [0] => A [1] => B ) )
We can see here that:
$a is an array, $a[0]=1, $a[1]=2 and $a[2]=array it self with two elements.
thx
dp

darthjarkon
I found a slightly better way to create large 2d arrays:
<?php
// this will simply output a 2d array-- it isn't very robust but it
//suits my needs here
function display_all($array){
echo "<table><tr>";
foreach($array as $spot){
echo "<td align='center' width= '20'>";
foreach($spot as $spotdeux){
echo "
".$spotdeux;
}
}
echo "</tr> </table>";
}
//this actually creates the array and puts the value 0 in all
// locations.  the $xax and $yax can be upped or
//downed to create a larger or smaller array
function creater_array(){
$ar=Array();
$xax=5;
$yax=5;
$i=1;
for ($y=0; $y<$yax; $y++)
{
array_push($ar,array());
for ($x=0; $x<$xax; $x++)
{
array_push($ar[$y],"0");
}
}
return $ar;
}
$b = creater_array();
display_all($b);
?>

matthiasdeletethis
How to use array() to create an array of references rather than of copies? (Especially needed when dealing with objects.) I played around somewhat and found a solution: place & before the parameters of array() that shall be references. My PHP version is 4.3.10.
Demonstration:
<?php
$ref1 = 'unchanged';
$ref2 = & $ref1;
$array_of_copies = array($ref1, $ref2);
print_r($array_of_copies); // prints: Array ( [0] => unchanged [1] => unchanged )
$array_of_copies[0] = 'changed'; // $ref1 = 'changed'; is not equivalent, as it was _copied_ to the array
print_r($array_of_copies); // prints: Array ( [0] => changed [1] => unchanged )
$array_of_refs = array(& $ref1, & $ref2); // the difference: place & before arguments
print_r($array_of_refs); // prints: Array ( [0] => unchanged [1] => unchanged )
$array_of_refs[0] = 'changed'; // $ref1 = 'changed'; is equivalent as $array_of_refs[0] references $ref1
print_r($array_of_refs, true); // prints: Array ( [0] => changed [1] => changed )
?>

madlogic
Heres a simple yet intelligent way of setting an array, grabbing the values from the array using a loop.
<?php
$ary = array("1"=>'One','Two',"3"=>'Three');
$a = '0'; $b = count($ary);
while ($a <= $b) {
 $pr = $ary[$a];
 print "$pr
";
 $a++;
}
?>

joshua dot e
Here's a cool tip for working with associative arrays-
Here's what I was trying to accomplish:
I wanted to hit a DB, and load the results into an associative array, since I only had key/value pairs returned. I loaded them into an array, because I wanted to manipulate the data further after the DB select, but I didn't want to hit the DB more than necessary.
Here's how I did it:
<?php
//assume db connectivity
//load it all into the associative array
$sql = "SELECT key,value FROM table";
$result = mysql_query($sql);
while($row = mysql_fetch_row($result)) {
$myArray[$row[0]] = $row[1];
}
//now we expand it
while(list($key,$value) = each($myArray)) {
echo "$key : $value";
}
?>
I found this to be super efficient, and extremely cool.

tcross1
here is the sort of "textbook" way to output the contents of an array which avoids using foreach() and allows you to index & iterate through the array as you see fit:
<?php
$arrayName = array("apples", "bananas", "oranges", "pears");
$arrayLength = count($arrayName);
for ($i = 0; $i < $arrayLength; $i++){
   echo "arrayName at[" . $i . "] is: [" .$arrayName[$i] . "]
\n";
}
?>
enjoy!
-tim

baghera
Every array has an "internal pointer". When you create an array, the internal pointer is automatically set to point at the first member. You can print the current location of the pointer:
$bob= current($myarrayname);
echo "$bob";
You can advance the pointer to the next spot using next($myarrayname).
To see a particular member of an array, set a $variable= $myarrayname[2] where "2" is the number of the member you want to use.
When assigning members to an array, the members are numbered beginning with 0, rather than 1.

bazz
Chek this out!!!. Suppose that you want to create an array like the following:
<?php
 $arr1 = (
   0 => array ("customer"=>"Client 1","Item a"),
   1 => array ("customer"=>"Client 2","Item b")
 );
?>
Seems prety easy, but what if you want to generate it dinamically woops!!!.  Imagine that you have a file with thousands of lines and each line is a purchase order from diferent clients:
<?php
/*function to add elements*/
function addArray(&$array, $id, $var)
{
   $tempArray = array( $var => $id);
   $array = array_merge ($array, $tempArray);
}
/*The same as above but the element is an array*/
function addArrayArr(&$array, $var, &$array1)
{
   $tempArray = array($var => $array1);
   $array = array_merge ($array, $tempArray);
}
/*labels of our array or heders of the file*/
$keyarr = array("customer","item");
/*info that may you read from a file line 1 and 2*/
$valarr0 = array("Client 1","Item a");
$valarr1 = array("Client 2","Item b");
$numofrows = 2;/*In our case is just two lines*/
$tmpArray = array();
for($i = 0; $i < $numofrows; $i++){
 $tmp = "valarr$i";
 $tmpvar = ${$tmp};/*Using var of vars tricky tricky*/
 foreach( $keyarr as $key=>$value){
   addArray($tmparr,$tmpvar[$key],$value);
 }
 addArrayArr($finalarr,$i,$tmparr);
} /*voila all it's perfectly ordered on finalarr*/
/*Here we just print the info but you can insert it into a database*/
echo "Customer: ".$finalarr[0]["customer"]."
";
echo "Item: ".$finalarr[0]["item"]."
";
echo "Customer: ".$finalarr[1]["customer"]."
";
echo "Item: ".$finalarr[1]["item"]."
";  
?>
The lines above should print something like:
Customer: Client 1
Item: Item a
Customer: Client 2
Item: Item b
I hope someone find this useful.

john
Be careful not to create an array on top of an already existing variable:
<?php
$name = "John";
$name['last'] = "Doe";
?>
$name becomes "Dohn" since 'last' evaluates to the 0th position of $name.
Same is true for multi-arrays.

mortoray
Be careful if you need to use mixed types with a key of 0 in an array, as several distinct forms end up being the same key:
$a = array();
$a[null] = 1;
$a[0] = 2;
$a['0'] = 3;
$a["0"] = 4;
$a[false] = 5;
$a[0.0] = 6;
$a[''] = 7;
$a[] = 8;
print_r( $a );
This will print out only 3 values: 6, 7, 8.

jasonr
Arrays are never removed from memory, however there is an internal pointer that always points to the "next" array item. After you interate through an array, this will need to be reset back to the first element if you want to access it in a loop again.
see the Reset function at
http://www.php.net/manual/function.reset.php if you are confused.

m dot izydorski
Ad. rdude's comment
Additionally, there is a performance loss while one are using ` marks instead ' when creating an array:
<?
//Very slow:
$my_array = array(`sign`, `cat01`, `cat02`, ... , `cat40`,`terra01`, `terra02`, ... , `terra50`);
//Much faster:
$my_array = array('sign', 'cat01', 'cat02', ... , 'cat40', 'terra01', 'terra02', ... , 'terra50');
?>
There is no reason to use ` marks (as I know), but this is a default question mark used in query output in phpMyAdmin. If you copy-paste phpMyAdmin query display, you can encounter serious performance problem.

grubby_d
About NULL as an array index.
An interesting thing with arrays is that you can use NULL as an index. I am trying it out with drop down list which will be used to update a database. Its not that good of an idea but it made me find the solution. For the database example you want to use the index "NULL" with quotes.
Say you have table person which has a foreign key reference to companies. BUT you want to allow the user to not specify a company as well. So you have determined that the database reference allows NULLs.
So you make a SELECT control with the lookup values as:
<OPTION value=(comp_id)>comp_name</OPTION>
using a while loop to print out the values.
Then you want the option to select NONE of the options. If you use something like -1 or 0 to represent this "blank" option you have to handle that in your php. Instead add this to your array: myarray("NULL") = "-none-" and you will get a field like this:
<OPTION value=NULL>-none-</OPTION>
Now every value from your SELECT control will be valid for the database and wont cause a foreign key references violation. it doesnt guarantee the data is coming from your trusty SELECT box so you still may want to check anyway.
Some interesting things about using the real NULL value as an array index:
<?php
$myarray = array(1, 2, 3);
echo count($myarray) . "
";  // 3
$myarray[NULL] = "the null value";
echo count($myarray) . "
";  // 4
if (array_key_exists(NULL, $myarray)
{ echo "this code will never be reached";}
?>
This will return FALSE and will generate this warning:
Warning: Wrong datatype for first argument in call to array_key_exists

justinbr
@Sam Yong - hellclanner [at] live dot com from below:
There's already a range() function - http://us.php.net/manual/en/function.range.php
It's used exactly like yours, plus it can do characters:
<?php
$values = range(1,1000); //$values = array(1,2,...,1000);
$values = range(100,1); //$values = array(100,99,...,1);
$values = range('a','z'); //$values = array('a','b',...,'z');
?>

jupiter
<?php
// changes any combination of multiarray elements and subarrays
// into a consistent 2nd level multiarray, tries to preserves keys
function changeMultiarrayStructure($multiarray, $asc = 1) {
 if ($asc == 1) {  // use first subarrays for new keys of arrays
   $multiarraykeys = array_reverse($multiarray, true);
 } else {  // use the last array keys
   $multiarraykeys = $multiarray;  // use last subarray keys
 }  // end array reordering
 $newarraykeys = array();  // establish array
 foreach ($multiarraykeys as $arrayvalue) {  // build new array keys
   if (is_array($arrayvalue)) {  // is subarray an array
     $newarraykeys = array_keys($arrayvalue) + $newarraykeys;
   }  // if count(prevsubarray)>count(currentarray), extras survive
 }  // end key building loop
 foreach ($multiarray as $newsubarraykey => $arrayvalue) {
   if (is_array($arrayvalue)) {  // multiarray element is an array
     $i = 0;  // start counter for subarray key
     foreach ($arrayvalue as $subarrayvalue) {  // access subarray
       $newmultiarray[$newarraykeys[$i]][$newsubarraykey] = $subarrayvalue;
       $i++;  // increase counter
     }  // end subarray loop
   } else {  // multiarray element is a value
     foreach ($newarraykeys as $newarraykey) {  // new subarray keys
       $newmultiarray[$newarraykey][$newsubarraykey] = $arrayvalue;
     }  // end loop for array variables
   }  // end conditional
 }  // end new multiarray building loop
 return $newmultiarray;
}
// will change
$old = array('a'=>1,'b'=>array('e'=>2,'f'=>3),'c'=>array('g'=>4),'d'=>5);
// to
$new = array('e'=>array('a'=>1,'b'=>2,'c'=>4,'d'=>5),
 'f'=>array('a'=>1,'b'=>3,'d'=>5));
// note: if $asc parameter isn't default, last subarray keys used
?>
The new key/value assignment pattern is clearer with bigger arrays.
I use this to manipulate input/output data from my db. Enjoy.

aissatya
<?php
$foo = array('bar' => 'baz');
echo "Hello {$foo['bar']}!"; // Hello baz!
?>
<?php
$firstquarter = array(1 => 'January', 'February', 'March');
print_r($firstquarter);
?>
<?php
$fruits = array (
  "fruits"  => array("a" => "orange", "b" => "banana", "c" => "apple"),
  "numbers" => array(1, 2, 3, 4, 5, 6),
  "holes"  => array("first", 5 => "second", "third")
);
?>

tobiasquinteiro
<?
       // This is a small script that shows how to use an multiple array
       for($x = 0;$x < 10;$x++){
               for($y = 0;$y < 10;$y++){
                       $mat[$x][$y] = "$x,$y";
               }
       }
       for($x = 0;$x < count($mat);$x++){
               for($y = 0;$y < count($mat[$x]);$y++){
                       echo    "mat[$x][$y]: " .
                               $mat[$x][$y] . " ";
               }
               echo "\n";
       }
?>

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