Each function in the manual is documented for quick reference. Knowing how to read and understand the text will make learning PHP much easier. Rather than relying on examples or cut/paste, everyone should know how to read function definitions (prototypes). Let's begin:
Note: Prerequisite: Basic understanding of types
Although PHP is a loosely typed language, it's important to have a basic understanding of types as they have important meaning.
Function definitions tell us what type of value is returned. Let's use the definition for strlen() as our first example:
strlen (PHP 4, PHP 5) strlen -- Get string length Description int strlen ( string $string ) Returns the length of given string.
Part | Description |
---|---|
strlen | The function name. |
(PHP 4, PHP 5) | strlen() has been around in all versions of PHP 4 and PHP 5 |
int | Type of value this function returns, which is an integer (i.e. the length of a string is measured in numbers). |
( string $string ) |
The first (and in this case the only) parameter/argument for this
function is named string , and it's a
string.
|
We could rewrite the above function definition in a generic way:
returned type function name ( parameter type parameter name )
Many functions take on multiple parameters, such as in_array(). Its prototype is as follows:
bool in_array ( mixed $needle, array $haystack [, bool $strict])
What does this mean? in_array() returns a
boolean value, TRUE
on
success (if the needle
was found in the
haystack
) or FALSE
on failure (if the
needle
was not found in the
haystack
). The first parameter is named
needle
and it can be of many different
types, so we call it
"mixed". This mixed needle
(what we're looking for) can be either a scalar value (string, integer,
or float), or an
array.
haystack
(the array we're searching in) is the
second parameter. The third optional parameter is
named strict
. All optional parameters are seen
in [ brackets ]. The manual
states that the strict
parameter defaults to
boolean FALSE
. See the manual page on each function for details on
how they work.
There are also functions with more complex PHP version information. Take html_entity_decode() as an example:
(PHP 4 >= 4.3.0, PHP 5)
This means that this function has only been available in a released version since PHP 4.3.0.