PHP/Operator/Comparison Operators — различия между версиями
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Admin (обсуждение | вклад) м (1 версия) |
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Текущая версия на 07:06, 26 мая 2010
Содержание
- 1 Comparing numbers and strings
- 2 Comparison Operators
- 3 Equality Operators in action
- 4 Equality Operators summary table
- 5 Loose Comparison Operators
- 6 The equality operator
- 7 These values are compared using dictionary order
- 8 These values are compared using numeric order
- 9 The Ternary Operator
- 10 Using Comparison Operators in if Statements
Comparing numbers and strings
<?
// These values are compared using dictionary order
if ("x54321" > "x5678") {
print "The string "x54321" is greater than the string "x5678".";
} else {
print "The string "x54321" is not greater than the string "x5678".";
}
Comparison Operators
example name result
$a == $b Equal True if $a is equal to $b.
$a === $b Identical True if $a is equal to $b, and they are of the same type. (PHP4 only)
$a != $b Not equal True if $a is not equal to $b.
$a < $b Less than True if $a is strictly less than $b.
$a > $b Greater than True if $a is strictly greater than $b.
$a <= $b Less than or equal to True if $a is less than or equal to $b.
$a >= $b Greater than or equal to True if $a is greater than or equal to $b.
<?php
$a = ("PHP"=="PHP")? "true":"false";
$b = ("PHP"=="PERL")?"true":"false";
$c = (1.785==1.785)? "true":"false";
$d = (5 != 5)?"true":"false";
$e = (true == true)?"true":"false";
$f = (false != false)?"true":"false";
$g = (100<200)?"true":"false";
$h = (100<100)?"true":"false";
$i = (100<=100)?"true":"false";
$j = ( -1 > 1 )?"true":"false";
$result = "TEST STRINGS \$a:$a \$b:$b<br>";
$result .= "TEST NUMBERS \$c:$c \$d:$d<br>";
$result .= "TEST BOOLEANS \$e:$e \$f:$f<br>";
$result .= "TEST LESS THAN \$g:$g \$h:$h<br>";
$result .= "TEST LESS THAN OR EQUAL \$i:$i<br>";
$result .= "TEST GREATER THAN \$j:$j";
?>
<html>
<head>
<title>Comparison Operators</title>
</head>
<body>
<?php echo( $result ); ?>
</body>
</html>
Equality Operators in action
<html>
<head>
<title>Equality</title>
</head>
<body>
<?php
$a = 1;
$b = "1";
print("(\$a == \$b)" . (($a == $b) ? "True" : "False") . "<br />");
print("(\$a != \$b)" . (($a != $b) ? "True" : "False") . "<br />");
print("(\$a === \$b)" . (($a === $b) ? "True" : "False") . "<br />");
print("(\$a !== \$b)" . (($a !== $b) ? "True" : "False") . "<br />");
?>
</body>
</html>
Equality Operators summary table
<!--
Operation Operator Example
Equality == $a == $b
Inequality != $a != $b
Inequality <> $a <> $b
Identity === $a === $b
Nonidentity !== $a !== $b
-->
Loose Comparison Operators
Example Name Description
$a == $b Equal to True if $ais equal to $b
$a != $b Not equal to True if $ais not equal to $b
$a < $b Less than True if $ais less than $b
$a > $b Greater than True if $ais greater than $b
$a <= $b Less than or equal to True if $ais less than or equal to $b
$a >= $b Greater than or equal to True if $a is greater than or equal to $b
$a === $b Equal to True if $ais equal to $b and they are of the same type
$a !== $b Not equal to True if $ais not equal to $bor they are not of the same type
The equality operator
<?
$new_messages = 10
if ($new_messages == 10) {
print "You have ten new messages.";
}
if ($new_messages == $max_messages) {
print "You have the maximum number of messages.";
}
if ($dinner == "B") {
print "B.";
}
?>
These values are compared using dictionary order
if ("6 p" < "55 c") {
print ""6 p" is less than than the string "55 c".";
} else {
print ""6 p" is not less than the string "55 c".";
}
These values are compared using numeric order
if ("6 p" < 55) {
print ""6 p" is less than the number 55.";
} else {
print ""6 p" is not less than the number 55.";
}
?>
The Ternary Operator
<?
$age = 18;
$agestr = ($age < 16) ? "child" : "adult";
?>
Using Comparison Operators in if Statements
<?php
$p = 14;
if ($p < 15) {
echo "Sorry! <BR>";
} else {
echo "Congratulations";
}
?>