In case you are just beginning to code in PHP and this is your first
experience in programming, the Modulus (%) is a great way to code photo
albums based on a table (it returns the remainder of integer divided by
integer). The modulus helps to wrap data to next row based on the result
of '$currentrow(from db)' % 'number of columns in database'. The only
thing to look out for is that 1 % 4 is 1, 2 % 4 is 2, etc. and not zero or
some other number, like you might think at first. Hope this will help some
newbie programmers like myself.

You can also use the floor() and ceil() functions to give the nearest
integer values of a double. So, for instance, to get the integer part of
the quotient, you can do this:

floor( $a / $b );

Normally, a negative value modulo a positive number generates a negaive
number, if you don't want that (for example, the number has to be between
0 and 9 and not negative) then you can use a function like this:
function mod($a,$b) 
{ 
if ($a <= 0) return (int) mod($b-abs($a), $b); else return (int) $a %
$b;
}
for example: 
-2 % 10 = -2
but mod(-2, 10) will return 8.

Yet another IWBNI posting...
I used the caret ( ^ ) "operator" in a truncate() function of
mine with a result similar to a substraction. So, I had to implement an
even weirder function which would work better. Should anyone know of a
better way to do this, I thank in advance.

//The function expects a double $num and an int $pos indicating the
decimal
//positions to allow

function truncate($num,$pos){
$pos=(int)$pos;
$m="1e$pos"; //this is our divider, ten at $pos power
$t=(double)$num*(double)$m; //just to be sure
$t=(int)$t; //yes, we need to cut superfluous decimals
$t=(double)$t/(double)$m;
return $t;
}

There are some operator descriptions missing. (I'm not sure what is
considered as operator in PHP, but anyway)

:: 
Scope resolution operator for class

->
Member selection operator for class

new
Object creation operator

?:
It is described in Comparison Operator Section. I think it worth to make a
new sub section for ternary operator.

[]
I think Array "[]" is considered as operator. It mentioned in
Operator Precedence Section as [, but no description. (Or is there any
other use for single "["?)

() 
Grouping expressions. It might not considered as operator in PHP, but it
is better to be included at least in Operator Precedence section.

{}
Resolve ambiguous reference to variables. For example, {} is needed to
resolve $array1['array_stored_as_array_element']['value']. {} is also
needed to resolve ambiguity such as echo " $array_3d[1][2][3] "
It might not considered as operator in PHP, but it is better to be
included at least in Operator Precedence section.

&
Reference operator. There is a section for reference, but it is better to
be explained briefly in this section and direct reader to Reference
section.

(type)
Cast operator like (int)$v to get integer value. I suppose these are
operators also. Mentioned in Precedence section, but no description.

+= -= *= /= .= %= &= |= ^= ~= <<= >>= 
Some assignment operators that are supported are not described. Mentioned
in Precedence section, though.

print
Looks like "print" is considered as operator in PHP. (I thought
"echo" is) It mentioned in Precedence section, but no
description. Description for these may be helpful for programmers to
distinguish what is "expression" and what is not.

  For some reason, PHP4.0.4pl1 dose not allow. (I posted as bug, I got
reply "echo" is not a valid expression. Therefore, PHP
complained for following code as a parse error)

($val) ? echo('true') : echo('false');

  but PHP does ALLOW

($val) ? print('true') : print('false');
($val) ? include('true.inc') : include('false.inc');

I'm confused with these. i.e. What is a expression, what is not an
expression.  

If there are other operators like "print" (maybe echo?), all of
them should be described or mentioned, at least, in this section. (I think
it would be nice to have a section describing what is statements/language
construct)

It is not about operator, but it would be nice to have BNF of PHP (Zend
Script Engine) as a reference.

For type casting is described at



(I suppose cast is operator, isn't it?)

There is no power-operator. Use pow() instead.

See:


There might come a power-operator in a future release, but that is still
being discussed

You can use the shorthand:

$a = 5;
$a += 10;    // $a is now 15
$a -= 3;    // $a is now 12

If this doesn't work:
($val) ? echo('true') : echo('false');
...you should use this:
if($val) { echo('true'); } else { echo('false'); }
...or, better yet, this:
echo($val ? 'true' : 'false');
...because $val, 'true', and 'false' are all expressions, but echo() is
not.

The "expr?expr:expr" operator is used to select between
expressions in the middle of a command. If you need to select between
different commands instead, it's probably better to use if() instead.
That's what it's there for.

The PHP modulus function will (interestingly) not return the decimal
portion of the result. I wrote a little function that will do so, and
mimics the results obtained by using the Windows calculator mod function:

function modphp($x, $y, $z) {

	for ($y = 0; $y <= abs($z); $y++) {
		$w = abs($z) - (abs($x) * $y);
		if ($w < abs($x)) {
			break;
		}		
	}	

	if ($z < 0) {
		return(-$w);
	} else {
		return($w);
	}

}

Here's how to pull the answer out of the mod function above:

$answer = modphp($var_x, $var_y, $var_z);

Remember that when you're reading from a socket, all output is of type
string.

Use ord() on each 'character', to get the byte values and use bitwise
arithmetics.

The =& operator can be found in section 14 -- returning references.