PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Using Functions in PHP
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Note that the syntax is slightly different from the same option in php.ini: As well as
php_value at the start of the line, there is no equal sign. A number of other php.ini
configuration settings can be altered in this way, too.
Setting options in the .htaccess file rather than in either php.ini or your web server’s
configuration file gives you a lot of flexibility.You can alter settings on a shared
machine that affect only your directories.You do not need to restart the web server, and
you do not need administrator access. A drawback to the .htaccess method is that the
files are read and parsed each time a file in that directory is requested rather than just
once at startup, so there is a performance penalty.
Using Functions in PHP
Functions exist in most programming languages; they separate code that performs a single,
well-defined task.This makes the code easier to read and allows you to reuse the
code each time you need to perform the same task.
A function is a self-contained module of code that prescribes a calling interface, performs
some task, and optionally returns a result.
You have seen a number of functions already. In preceding chapters, we routinely
called a number of the functions built into PHP.We also wrote a few simple functions
but glossed over the details. In the following sections, we cover calling and writing functions
in more detail.
Calling Functions
The following line is the simplest possible call to a function:
function_name();
This line calls a function named function_name that does not require parameters.This
line of code ignores any value that might be returned by this function.
A number of functions are called in exactly this way.The function phpinfo() is often
useful in testing because it displays the installed version of PHP, information about PHP,
the web server setup, and the values of various PHP and server variables.This function
does not take any parameters, and you generally ignore its return value, so a call to
phpinfo() is written as follows:
phpinfo();
Most functions, however, do require one or more parameters, which are the inputs to
functions.You pass parameters by placing data or the name of a variable holding data
inside parentheses after the function name.You could call a function that accepts a single
parameter as follows:
function_name(‘parameter’);