PHP supports the following types:
The type of a variable is usually not set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.
If you would like to force a variable to be converted to a certain type, you may either cast the variable or use the settype() function on it.
Note that a variable may behave in different manners in certain situations, depending on what type it is a the time. For more information, see the section on Type Juggling.
Integers can be specified using any of the following syntaxes:
$a = 1234; # decimal number $a = -123; # a negative number $a = 0123; # octal number (equivalent to 83 decimal) $a = 0x12; # hexadecimal number (equivalent to 18 decimal)
Floating point numbers ("doubles") can be specified using any of the following syntaxes:
$a = 1.234; $a = 1.2e3;
Strings can be specified using one of two sets of delimiters.
If the string is enclosed in double-quotes ("), variables within the string will be expanded (subject to some parsing limitations). As in C and Perl, the backslash ("\") character can be used in specifying special characters:
Table 5-1. Escaped characters
| sequence | meaning |
|---|---|
| \n | newline |
| \r | carriage |
| \t | horizontal tab |
| \\ | backslash |
| \$ | dollar sign |
| \" | double-quote |
You can escape any other character, but a warning will be issued at the highest warning level.
The second way to delimit a string uses the single-quote ("'") character, which does not do any variable expansion or backslash processing (except for "\\" and "\'" so you can insert backslashes and single-quotes in a singly-quoted string).
Arrays actually act like both hash tables (associative arrays) and indexed arrays (vectors).
PHP supports both scalar and associative arrays. In fact, there is no difference between the two. You can create an array using the list() or array() functions, or you can explicitly set each array element value.
$a[0] = "abc";
$a[1] = "def";
$b["foo"] = 13;
You can also create an array by simply adding values to the array.
$a[] = "hello"; // $a[2] == "hello"
$a[] = "world"; // $a[3] == "world"
Arrays may be sorted using the asort(), arsort(), ksort(), rsort(), sort(), uasort(), usort(), and uksort() functions depending on the type of sort you want.
You can count the number of items in an array using the count() function.
You can traverse an array using next() and prev() functions. Another common way to traverse an array is to use the each() function.
Multi-dimensional arrays are actually pretty simple. For each dimension of the array, you add another [key] value to the end:
$a[1] = $f; # one dimensional examples
$a["foo"] = $f;
$a[1][0] = $f; # two dimensional
$a["foo"][2] = $f; # (you can mix numeric and associative indices)
$a[3]["bar"] = $f; # (you can mix numeric and associative indices)
$a["foo"][4]["bar"][0] = $f; # four dimensional!
You can "fill up" multi-dimensional arrays in many ways, but the trickiest one to understand is how to use the array() command for associative arrays. These two snippets of code fill up the one-dimensional array in the same way:
# Example 1:
$a["color"] = "red";
$a["taste"] = "sweet";
$a["shape"] = "round";
$a["name"] = "apple";
$a[3] = 4;
# Example 2:
$a = array(
"color" => "red",
"taste" => "sweet",
"shape" => "round",
"name" => "apple",
3 => 4
);
The array() function can be nested for multi-dimensional arrays:
<?
$a = array(
"apple" => array(
"color" => "red",
"taste" => "sweet",
"shape" => "round"
),
"orange" => array(
"color" => "orange",
"taste" => "sweet",
"shape" => "round"
),
"banana" => array(
"color" => "yellow",
"taste" => "paste-y",
"shape" => "banana-shaped"
)
);
echo $a["apple"]["taste"]; # will output "sweet"
?>
To initialize an object, you use the new statement to instantiate the object to a variable.
class foo {
function do_foo () {
echo "Doing foo.";
}
}
$bar = new foo;
$bar -> do_foo ();