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.
strlen (PHP 4, PHP 5) strlen -- Get string length Description int strlen ( string $string ) Returns the length of given string.
|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
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 = FALSE ] )
What does this mean? in_array() returns a
success (if the
needle was found in the
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
(what we're looking for) can be either a scalar value (string, integer,
or float), or an
haystack (the array we're searching in) is the
second parameter. The third optional parameter is
strict. All optional parameters are seen
in [ brackets ]. The manual
states that the
strict parameter defaults to
FALSE. See the manual page on each function for details on
how they work.
In addition the & (ampersand) symbol prepended to a function parameter allows the parameter to be passed by reference, as seen below:
int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )
In this example, we can see the third optional parameter
&$matches will be
passed as reference.
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.