Php Chapter 2 3 Training

PHP Functions
and
Arrays
Orlando PHP Meetup
Zend Certification Training
March 2009

Functions
Minimal syntax
function name() { }
PHP function names are not case-
sensitive.
All functions in PHP return a value—even
if you don’t explicitly cause them to.
No explicit return value returns NULL
“return $value;” exits function immediately.

Variable Scope
Global scope
A variable declared or first used outside of a function or
class has global scope.
NOT visible inside functions by default.
Use “global $varname;” to make a global variable visible
inside a function.
Function scope
Declared or passed in via function parameters.
A visible throughout the function, then discarded when
the function exits.
Case scope
Stay tuned for Object Oriented chapter…

Scope (continued)
Global
$a = "Hello";
$b = "World";
function hello() {
global $a, $b;
echo "$a $b";
echo $GLOBALS[’a’] .’ ’.
$GLOBALS[’b’];
}

Scope (continued)
Regular Parameters
function hello($who = "World") {
echo "Hello $who";
}
Variable Length Parameters
func_num_args(), func_get_arg() and
func_get_args()
function hello() {
if (func_num_args() > 0) {
$arg = func_get_arg(0); // The
first argument is at position 0
echo "Hello $arg";
} else {
echo "Hello World";
}

Passing Arguments by
ReferencePrefix a parameter with an “&”
Function func (&$variable) {}
Changes to the variable will persist after the function
call
function cmdExists($cmd, &$output =
null) {
$output = ‘whereis $cmd‘;
if (strpos($output,
DIRECTORY_SEPARATOR) !== false) {
return true;
} else {
return false;
}
}

Function Summary
Declare functions with parameters and
return values
By default, parameters and variables have
function scope.
Pass parameters by reference to return
values to calling function.
Parameters can have default values. If no
default identified, then parameter must be
passed in or an error will be thrown.
Parameter arrays are powerful but hard to
debug.

Arrays
All arrays are ordered collections of
items, called elements.
Has a value, identified by a unique key (integer
or case sensitive string)
Keys
By default, keys start at zero
String can be of any length
Value can be any variable type (string,
number, object, resource, etc.)

Declaring Arrays
Explicit
$a = array (10, 20, 30);
$a = array (’a’ => 10, ’b’ =>
20, ’cee’ => 30);
$a = array (5 => 1, 3 => 2, 1
=> 3,);
$a = array(); //Empty
Implicit
$x[] = 10; //Gets next
available int index, 0
$x[] = 11; //Next index, 1
$x[’aa’] = 11;

Printing Arrays
print_r()
Recursively prints the values
May return value as a string to assign to a
variable.
Var_dump()
outputs the data types of each value
Can only echo immediately

Enumerative vs.
Associative
Enumerative
Integer indexes, assigned sequentially
When no key given, next key = max(integer keys) + 1
Associative
Integer or String keys, assigned specifically
Keys are case sensitive but type insensitive
‘a’ != ‘A’ but ‘1’ == 1
Mixed
$a = array (’4’ => 5, ’a’ => ’b’);
$a[] = 44; // This will have a key of 5

Multi-dimensional
Arrays
Array item value is another array
$array = array();
$array[] = array(’foo’,’bar’);
$array[] = array(’baz’,’bat’);
echo $array[0][1] . $array[1]
[0];

Unraveling Arrays
list() operator
Receives the results of an array
List($a, $b, $c) = array(‘one’, ‘two’, ‘three’);
Assigns $a = ‘one’, $b = ‘two’, $c = ‘three’
Useful for functions that return an array
list($first, $last,
$last_login) =
mysql_fetch_row($result);

Comparing Arrays
Equal (==)
Arrays must have the same number and value
of keys and values, but in any order
Exactly Equal (===)
Arrays must have the same number and value
of keys and values and in the exact same order.

Counting, Searching
and Deleting Elements
count($array)
Returns the number of elements in the first
level of the array.
array_key_exists($key, $array)
If array element with key exists, returns
TRUE, even if value is NULL
in_array($value, $array)
If the value is in the array, returns TRUE
unset($array[$key])
Removes the element from the array.

Flipping and Reversing
array_flip($array)
Swaps keys for values
Returns a new array
array_reverse($array)
Reverses the order of the key/value pairs
Returns a new array
Don’t confuse the two, like I usually do

Array Iteration
The Array Pointer
reset(), end(), next(), prev(), current(), key()
An Easier Way to Iterate
foreach($array as $value) {}
foreach($array as $key=>$value){}
Walk the array and process each value
array_walk($array, ‘function name to call’);
array_walk_recursive($array, ‘function’);

Sorting Arrays
There are eleven sorting functions in PHP
sort($array)
Sorts the array in place and then returns.
All keys become integers 0,1,2,…
asort($array)
Sorts the array in place and returns
Sorts on values, but leaves key assignments in
place.
rsort() and arsort() to reverse sort.
ksort() and krsort() to sort by key, not value

Sorting (continued)
usort($array, ‘compare_function’)
Compare_function($one, $two) returns
-1 if $one < $two
0 if $one == $two
1 if $one > $two
Great if you are sorting on a special function,
like length of the strings or age or something
like that.
uasort() to retain key=>value association.
shuffle($array) is the anti-sort

Arrays as Stacks,
Queues and Sets
Stacks (Last in, first out)
array_push($array, $value [, $value2] )
$value = array_pop($array)
Queue (First in, first out)
array_unshift($array, $value [, $value2] )
$value = array_shift($array)
Set Functionality
$array = array_diff($array1, $array2)
$array = array_intersect($a1, $a2)

Summary
Arrays are probably the single most
powerful data management tool available
to PHP developers. Therefore, learning to
use them properly is essential for a good
developer.
Some methods are naturally more
efficient than others. Read the function
notes to help you decide.
Look for ways in your code to use arrays
to reduce code and improve flexibility.

Thank You
Shameless Plug
15 years of development experience, 14 of that
running my own company.
I am currently available for new contract work
in PHP and .NET.
cchubb@codegurus.com

Php Chapter 2 3 Training

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Php Chapter 2 3 Training