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How to read a function definition (prototype)

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, you will want

to know how to read function definitions (prototypes). Let's begin:

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 3, PHP 4, PHP 5)
strlen -- Get string length
Description
int strlen (string str)
Returns the length of 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 was not available in PHP 3, and is only

available in a released version since PHP 4.3.0.

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Отвечу на любые вопросы. С уважением, Дмитрий Владимирович.