PHP/Statement/If statement — различия между версиями

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Текущая версия на 07:07, 26 мая 2010

A helpful addition to if statements is the elseif statement, which allows you to chain conditions together in a more intelligent way:

 
<?php
            if ($Age < 10) {
                    print "You"re under 10";
            } elseif ($Age < 20) {
                    print "You"re under 20";
            } elseif ($Age < 30) {
                    print "You"re under 30";
            } elseif ($Age < 40) {
                    print "You"re under 40";
            } else {
                    print "You"re over 40";
            }
    ?>



An if Statement

 
<html>
<head><title>An if Statement</title></head>
<body>
<div>
<?php
    $satisfied = "very";
    if ( $satisfied == "very" ) {
      print "very";
    }
?>
</div>
</body>
</html>



An if Statement for string

<html>
<head>
<title>An if Statement</title>
</head>
<body>
<?php
$mood = "happy";
if ( $mood == "happy" ){
    print "I"m in a good mood";
}
?>
</body>
</html>



An if Statement That Uses else

 
<html>
<head>
<title>An if Statement That Uses else</title>
</head>
<body>
<div>
<?php
    $satisfied = "very";
    if ( $satisfied == "very" ) {
      print "very";
    } else {
      print "not very";
    }
?>
</div>
</body>
</html>



An if statement That Uses else and else if

 
<html>
<head>
<title>An if statement That Uses else and else if</title>
</head>
<body>
<div>
<?php
    $satisfied = "no";
    if ( $satisfied == "very" ) {
      print "very";
    } else if ( $satisfied == "no")  {
      print "no";
      // request further feedback
    } else {
      print "else";
    }
?>
</div>
</body>
</html>



Basic Use of the if Statement

 
<?php
    if (true) echo "This will always display!<BR>";
    if (false) {
        echo "This will never, ever be displayed.<BR>";
    } else {
        echo "This too will always display!<BR>";
    }
?>



Case Switching

 
<?php
            $Name = "Bob";
            if ($Name =  = "Jim") {
                    print "Your name is Jim\n";
            } elseif ($Name =  = "Bob") {
                    print "Your name is Bob\n";
            } else {
                    print "I don"t know your name!\n";
            }
    ?>



Checking multiple conditions

 
<?
if ($username == "Admin"){
    echo ("Welcome to the admin page.");
}
elseif ($username == "Guest"){
    echo ("Please take a look around.");
}
else {
    echo ("Welcome back, $username.");
}
?>



Executing Multiple Statements with One if

<?
$sky_color = "blue";
if($sky_color == "blue") {
     print("A <br/>");
     print("B <br/>");
}
print("Here I am.");
?>



If-else Statement

 
<html>
 <head>
  <title>If-else Statement</title>
 </head>
 <body>
 <?php
  $num = 2; 
  $bool=false;
  
  if($num==1 and $bool==true) echo("Test 1 success");
  else
  if($num==2 and $bool==true) echo("Test 2 success");
  else
  if($num==2 and $bool==false) echo("Test 3 success");
  else
  if($num==3 and $bool==false) echo("Test 4 success");
 ?>
 </body>
</html>



In if statement use OR to connect two conditions

<?
$degrees = "95";
$hot = "yes";
if (($degrees > 100) || ($hot == "yes")) {
    echo "<P>TESTIt"s <strong>really</strong> hot!</P>";
} else {
    echo "<P>TESTIt"s bearable.</P>";
}
?>



Making a decision with if()

 
<?
$logged_in = true;
if ($logged_in) {
   print "Welcome aboard, trusted user.";
}
?>



Multiconditional if Statements

 
<?php
    $finished = true;
    $complete = 14;
    if ( ($complete >= 15) || $finished)) {
        echo "get some sleep!<BR>";
    } else {
        echo "no sleep tonight!<BR>";
    }
?>



Multiple statements in an if() code block

 
<?
print "This is always printed.";
$logged_in = true;
if ($logged_in) {
    print "Welcome aboard, trusted user.";
    print "This is only printed if $logged_in is true.";
}
print "This is also always printed.";
?>



Print the string "Child message" if the $age variable is between 1 and 17

 
<?
$age = 12;
if ( $age >= 18 && $age <= 35 ) {
  print "Youth message<br />\n";
} else if ( $age >= 1 && $age <= 17 ) {
   print "Child message<br />\n";
} else {
  print "Generic message<br />\n";
}
?>



Use and to connect two statement in if statement

<?
$degrees = "95";
$hot = "yes";
if (($degrees > 100) && ($hot == "yes")) {
    echo "<P>TESTIt"s <strong>really</strong> hot!</P>";
} else {
    echo "<P> TESTIt"s bearable.</P>";
}
?>



Using elseif()

 
<?
$logged_in = true;
if ($logged_in) {
    print "Welcome aboard, trusted user.";
} elseif ($new_messages) {
    print "Dear stranger, there are new messages.";
} elseif ($emergency) {
    print "Stranger, there are no new messages, but there is an emergency.";
}
?>



Using else with if()

 
<?
$logged_in = true;
if ($logged_in) {
    print "Welcome aboard, trusted user.";
} else {
    print "Howdy, stranger.";
}
?>



Using if Statements to Mimic a select Statement

 
<?php
    
    $i = 0;
     
    if($i == 0) echo "First case";
    if($i == 1) echo "Second case";
    switch($i) {
        case 0:
            echo "First case";
            break;
        case 1:
            echo "Second case";
            break;
    }
?>



Using if statement to print "Youth message" if $age is between 18 and 35

 
<?
$age = 22;
if ( $age >= 18 && $age <= 35 ) {
  print "Youth message<br />";
} else {
  print "Generic message<br/>";
}
?>



Using if to test for multiple values

 
<?
$action = "ADD";
if ($action == "ADD") {
    echo "Perform actions for adding.";
}
elseif ($action == "MODIFY") {
    echo "Perform actions for modifying.";
}
elseif ($action == "DELETE") {
    echo "Perform actions for deleting.";
}
?>



Within an if Else statement

<?
$a = 21;
$b = 15;
echo "<P>Original value of \$a is $a and \$b is $b</P>";

if ($a == $b) {
    echo "<P>TEST\$a equals \$b</P>";
} else {
    echo "<P>TEST\$a is not equal to \$b</P>";
}
?>
Источник — «http://wbex.ru/index.php?title=PHP/Statement/If_statement&oldid=1275»