PHP/Operator/Arithmetic Operators — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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Текущая версия на 07:06, 26 мая 2010
Содержание
- 1 An example of PHP"s automatic type conversion is the addition operator "+".
- 2 Arithmetical Operators
- 3 Arithmetic Operators
- 4 Calculation Results for Postfix and Prefix Operators
- 5 Changing the default precedence using parentheses
- 6 Increment/decrement Operators
- 7 Incrementing and decrementing
- 8 Peculiarities of the ++ and -- Operators
- 9 postfix and prefix increment operators also work on letter values
- 10 Postfix and Prefix Operators in Action
- 11 Postfix and Prefix Operators summary table
- 12 Shorthand Operators summary table
- 13 Using Assignment Operators
- 14 Using autoincrement to add to a variable
- 15 Using pre- and postincrement
- 16 Using the autodecrement operator
- 17 Using the negation operator
- 18 Variables Are Assigned by Value
An example of PHP"s automatic type conversion is the addition operator "+".
<?
$foo = "0";
$foo++;
$foo += 1;
$foo = $foo + 1.3;
$foo = 5 + "10 L";
$foo = 5 + "10 S";
?>
Arithmetical Operators
<?php
$addnum = 20+30;
$addstr="I love "."PHP";
$sub = 35.75 - 28.25;
$mul = 8 * 50;
$mod = 65 % 2;
$inc = 5; $inc = ++$inc;
$dec = 5; $dec = --$dec;
$result = "addnum:$addnum <br>";
$result .= "addstr:$addstr <br>";
$result .= "sub:$sub <br>";
$result .= "mul:$mul <br>";
$result .= "mod:$mod <br>";
$result .= "inc:$inc <br>";
$result .= "dec:$dec <br>";
?>
<html>
<head>
<title>Arithmetical Operators</title>
</head>
<body>
<h3> <?php echo($result); ?> </h3>
</body>
</html>
Arithmetic Operators
Example Operation Result
-$a Negation Negative value of $a
$a + $b Addition Sum of $a and $b
$a - $b Subtraction Difference of $a and $b
$a * $b Multiplication Product of $a and $b
$a / $b Division Quotient of $a and $b
$a % $b Modulus Remainder of $a divided by $b
Calculation Results for Postfix and Prefix Operators
<?
$count = 0;
$result = $count++;
print("Post ++: count is $count, result is $result<BR>");
$count = 0;
$result = ++$count;
print("Pre ++: count is $count, result is $result<BR>");
$count = 0;
$result = $count--;
print("Post --: count is $count, result is $result<BR>");
$count = 0;
$result = --$count;
print("Pre --: count is $count, result is $result<BR>");
?>
Changing the default precedence using parentheses
<?
echo 2 * 3 + 4 + 1;
echo 2 * (3 + 4 + 1);
?>
Increment/decrement Operators
example name effect
++$a Pre-increment Increments $a by one, then returns$a.
$a++ Post-increment Returns $a, then increments $a by one.
�$a Pre-decrement Decrements $a by one, then returns $a.
$a� Post-decrement Returns $a, then decrements $a by one.
Incrementing and decrementing
<?
$birthday = $birthday + 1;
// Add another one to $birthday
++$birthday;
// Subtract 1 from $years_left
$years_left = $years_left - 1;
// Subtract another 1 from $years_left
--$years_left;
?>
Peculiarities of the ++ and -- Operators
<?
$b=true;
echo "b: $b<br>";
$b++;
echo "b: $b<br>";
?>
postfix and prefix increment operators also work on letter values
<?php
$a = "G98";
print("\$a = \"" . ++$a . "\"<br />");
print("\$a = \"" . ++$a . "\"<br />");
print("\$a = \"" . ++$a . "\"<br />");
?>
Postfix and Prefix Operators in Action
<html>
<head>
<title>Postfix and Prefix Operators</title>
</head>
<body>
<?php
$a = 5;
print("\$a = " . $a++ . "<br />");
print("\$a = " . ++$a . "<br />");
print("\$a = " . $a . "<br />");
print("\$a = " . $a. "<br />");
?>
</body>
</html>
Postfix and Prefix Operators summary table
Operation Operator Class Example
-----------------------------------------------------------------------------------------
Preincrement:
Increment operand by one before the variable is used. ++ Prefix ++$a
Postincrement:
Increment operand by one after the variable is used. ++ Postfix $a++
Predecrement:
Decrement operator by one before the variable is used. -- Prefix --$a
Postdecrement:
Decrement operand by one after the variable is used. -- Postfix $a--
Shorthand Operators summary table
Operation Operator Example Expansion
Assignment = $a = 5 $a = 5
Addition += $a += 5 $a = $a + 5
Subtraction -= $a -= 5 $a = $a - 5
Multiplication *= $a *= 5 $a = $a * 5
Division /= $a /= 5 $a = $a / 5
Concatenation .= $a .= "Add" $a = $a . "Add"
Modulus %= $a %= 5 $a = $a % 5
Bitwise AND &= $a &= 5 $a = $a & 5
Bitwise |= $a |= 5 $a = $a | 5
inclusive OR
Bitwise ^= $a ^= 5 $a = $a ^ 5
exclusive OR (XOR)
Bitwise NOT ~= $a ~= 5 $a = $a ~ 5
Bitwise <<= $a <<= 5 $a = $a << 5
left-shift
Bitwise >>= $a >>= 5 $a = $a >> 5
right-shift
Using Assignment Operators
<?
$origVar = 100;
echo "<P>Original value is $origVar</P>";
?>
Using autoincrement to add to a variable
<?php
$counter=1;
$counter++;
echo $counter
?>
Using pre- and postincrement
<?php
$test=1;
echo "Preincrement: ".(++$test);
echo "<BR>";
echo "Value afterwords: ".$test;
echo "<BR>";
$test=1;
echo "Postincrement: ".($test++);
echo "<BR>";
echo "Value afterwords: ".$test;
?>
Using the autodecrement operator
<?php
$counter=1;
$counter--;
echo $counter
?>
Using the negation operator
<?
$finished = false;
if ($finished == false) {
print "Not done yet!";
}
if (! $finished) {
print "Not done yet!";
}
?>
Variables Are Assigned by Value
<html>
<head>
<title>Variables are assigned by value</title>
</head>
<body>
<?php
$aVariable = 42;
$anotherVariable = $aVariable;
$aVariable = 325;
print $anotherVariable;
?>
</body>
</html>