Here's some good links accumulated from the answers below/Found myself for understanding the OO architecture/Unique Features in PHP, of course, it is meant for people from other areas like java and .net to have an overview of PHP features.
OO
Using namespace
http://php.net/manual/en/language.namespaces.basics.php
Fallback for global namespace
http://www.php.net/manual/en/language.namespaces.fallback.php
Class(overidden class, Const, static class) using ::
http://php.net/manual/en/language.oop5.paamayim-nekudotayim.php
Array
http://php.net/manual/en/language.types.array.php
An
array can be created using the
array() language construct. It takes any number of comma-separated
key => value pairs as arguments.
array(
key => value,
key2 => value2,
key3 => value3,
...
)
the
key can either be an
integer or a
string. The
value can be of any type.
Additionally the following key casts will occur:
- Strings containing valid integers will be cast to the integer type. E.g. the key "8" will actually be stored under 8. On the other hand "08" will not be cast, as it isn't a valid decimal integer.
- Floats are also cast to integers, which means that the fractional part will be truncated. E.g. the key 8.7 will actually be stored under 8.
- Bools are cast to integers, too, i.e. the key true will actually be stored under 1 and the key false under 0.
- Null will be cast to the empty string, i.e. the key null will actually be stored under "".
- Arrays and objects can not be used as keys. Doing so will result in a warning: Illegal offset type.
If multiple elements in the array declaration use the same key, only the last one will be used as all others are overwritten.
Example #2 Type Casting and Overwriting example
<?php
$array = array(
1 => "a",
"1" => "b",
1.5 => "c",
true => "d",
);var_dump($array);?>
The above example will output:
array(1) {
[1]=>
string(1) "d"
}
The
key is optional. If it is not specified, PHP will use the increment of the largest previously used
integer key.
Example #4 Indexed arrays without key
<?php
$array = array("foo", "bar", "hallo", "world");var_dump($array);?>
The above example will output:
array(4) {
[0]=>
string(3) "foo"
[1]=>
string(3) "bar"
[2]=>
string(5) "hallo"
[3]=>
string(5) "world"
}
It is possible to specify the key only for some elements and leave it out for others:
Example #5 Keys not on all elements
<?php
$array = array(
"a",
"b",
6 => "c",
"d",
);var_dump($array);?>
The above example will output:
array(4) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[6]=>
string(1) "c"
[7]=>
string(1) "d"
}
Multidimentional array
Accessing array elements with square bracket syntax
Array elements can be accessed using the array[key] syntax.
Example #6 Accessing array elements
<?php
$array = array(
"foo" => "bar",
42 => 24,
"multi" => array(
"dimensional" => array(
"array" => "foo"
)
)
);var_dump($array["foo"]);var_dump($array[42]);var_dump($array["multi"]["dimensional"]["array"]);?>
The above example will output:
string(3) "bar"
int(24)
string(3) "foo"
Creating/modifying with square bracket syntax
An existing
array can be modified by explicitly setting values in it.
This is done by assigning values to the
array, specifying the key in brackets. The key can also be omitted, resulting in an empty pair of brackets (
[]).
$arr[key] = value;
$arr[] = value;
// key may be an integer or string
// value may be any value of any type
If
$arr doesn't exist yet, it will be created, so this is also an alternative way to create an
array. This practice is however discouraged because if
$arr already contains some value (e.g.
string from request variable) then this value will stay in the place and
[] may actually stand for
string access operator. It is always better to initialize variable by a direct assignment.
To change a certain value, assign a new value to that element using its key. To remove a key/value pair, call the
unset() function on it.
Multidimentional array
Accessing array elements with square bracket syntax
Array elements can be accessed using the array[key] syntax.
Example #6 Accessing array elements
<?php
$array = array(
"foo" => "bar",
42 => 24,
"multi" => array(
"dimensional" => array(
"array" => "foo"
)
)
);var_dump($array["foo"]);var_dump($array[42]);var_dump($array["multi"]["dimensional"]["array"]);?>
The above example will output:
string(3) "bar"
int(24)
string(3) "foo"
Note:
Both square brackets and curly braces can be used interchangeably for accessing array elements (e.g. $array[42] and $array{42} will both do the same thing in the example above).
Useful functions
There are quite a few useful functions for working with arrays. See the
array functions section.
Note:
The
unset() function allows removing keys from an
array. Be aware that the array will
not be reindexed. If a true "remove and shift" behavior is desired, the
array can be reindexed using the
array_values() function.
The
foreach control structure exists specifically for
arrays. It provides an easy way to traverse an
array.
Regarding modification of the array:
http://stackoverflow.com/questions/5179606/php-replace-array-value
Note
Array assignment always involves value copying. Use the
reference operator to copy an
array by reference.
Include and require
http://www.php.net/manual/en/function.include.php
require is identical to include except upon failure it will also produce a fatal E_COMPILE_ERROR level error. In other words, it will halt the script whereas includeonly emits a warning (E_WARNING) which allows the script to continue.
foreach
The foreach construct provides an easy way to iterate over arrays. foreach works only on arrays and objects,
foreach (array_expression as $value)
statement
foreach (array_expression as $key => $value)
statement
<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
$value = $value * 2;
}// $arr is now array(2, 4, 6, 8)unset($value); // break the reference with the last element?>
Reference of a $value and the last array element remain even after the foreach loop. It is recommended to destroy it by unset().
You may have noticed that the following are functionally identical:
<?php
$arr = array("one", "two", "three");reset($arr);
while (list(, $value) = each($arr)) {
echo "Value: $value<br />\n";
}
foreach ($arr as $value) {
echo "Value: $value<br />\n";
}?>
