PHP/Data Type/Casting — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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(нет различий)
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Версия 10:37, 26 мая 2010
Содержание
- 1 Casting a Variable
- 2 Casting the return value
- 3 Change the data type
- 4 Changing Type by Casting
- 5 Converting to in parentheses before our variable name
- 6 Convert String to Date
- 7 convert to float
- 8 Force to change the data type by adding (int), (integer), (float), (double), or (real) in front of the variable
- 9 Maintaining the integrity of the data and outputting the end result.
- 10 Typecasting
- 11 Type conversion: Approach 1
- 12 Type conversion: Approach 2
- 13 Type conversion: approach 3
- 14 Type conversions
- 15 When the first expression is a string, the type of the variable will depend on the second expression.
Casting a Variable
<html>
<head>
<title>Casting a variable</title>
</head>
<body>
<?php
$undecided = 3.14;
$holder = ( double ) $undecided;
print gettype( $holder ) ;
print " -- $holder<br>";
$holder = ( string ) $undecided;
print gettype( $holder );
print " -- $holder<br>";
$holder = ( integer ) $undecided;
print gettype( $holder );
print " -- $holder<br>";
$holder = ( double ) $undecided;
print gettype( $holder );
print " -- $holder<br>";
$holder = ( boolean ) $undecided;
print gettype( $holder );
print " -- $holder<br>";
?>
</body>
</html>
Casting the return value
class TextInput {
public function __toString() {
return (string) $this->label;
}
}
Change the data type
<?php
$a = 123;
echo "is_int($a) = " . (is_int($a) ? "true" : "false") . "\n";
$a = "123";
echo "is_int((int)$a) = " . (is_int((int)$a) ? "true" : "false") . "\n";
?>
Changing Type by Casting
<html>
<body>
<div>
<?php
$undecided = 3.14;
$holder = ( double ) $undecided;
print gettype( $holder ) ;
print " -- $holder<br />";
$holder = ( string ) $undecided;
print gettype( $holder );
print " -- $holder<br />";
$holder = ( integer ) $undecided;
print gettype( $holder );
print " -- $holder<br />";
$holder = ( double ) $undecided;
print gettype( $holder );
print " -- $holder<br />";
$holder = ( boolean ) $undecided;
print gettype( $holder );
print " -- $holder<br />";
?>
</div>
</body>
</html>
Converting to in parentheses before our variable name
<?
$bool = true;
print "Bool is set to $bool\n";
$bool = false;
print "Bool is set to ";
print (int)$bool;
?>
Convert String to Date
<HTML>
<BODY>
<FORM METHOD="POST" ACTION="CallMe.php">
<TABLE>
<TR>
Date:<BR>
<TD><INPUT TYPE="TEXT" NAME="DATE" VALUE="<?php echo $DATE ?>"></TD>
</TR>
<TR>
<TD ALIGN="CENTER">+</TD>
</TR>
<TR>
<TD><INPUT TYPE="TEXT" NAME="OFFSET" VALUE="<?php echo $OFFSET ?>"></TD>
</TR>
<TR>
<TD ALIGN="CENTER"><INPUT TYPE="SUBMIT" VALUE="="></TD>
</TR>
<TR>
<TD><INPUT TYPE="TEXT" NAME="RESULT"
VALUE="<?php echo date("M j, Y",(strtotime($DATE)+60*60*24*($OFFSET))) ?>" disabled></TD>
</TR>
</TABLE>
</FORM>
</BODY>
</HTML>
convert to float
<?php
$val = 45678945939390393678976;
echo $val + 5;
?>
Force to change the data type by adding (int), (integer), (float), (double), or (real) in front of the variable
or value or by using the function intval() or floatval()
<?php
$a = 123;
echo "is_int($a) = " . (is_int($a) ? "true" : "false") . "\n";
$a = "123";
echo "is_int((int)$a) = " . (is_int((int)$a) ? "true" : "false") . "\n";
?>
Maintaining the integrity of the data and outputting the end result.
<?php
$myint = 10;
echo $myint . "<br />";
echo (int) $myint . "<br />";
$myint = 10 / 3;
echo (int) $myint . "<br />";
$thenumber = 9.99 * 1.07;
echo "$" . $thenumber . "<br />";
echo "$" . sprintf ("%.2f", $thenumber);
?>
Typecasting
<?php
$a = "10";
$b = (int)$a;
echo "gettype($a) = " . gettype($a) . "\n";
echo "gettype($b) = " . gettype($b) . ", \$b = $b\n";
$a = array(5,4,5);
$b = (int)$a;
echo "gettype($a) = " . gettype($a) . "\n";
echo "gettype($b) = " . gettype($b) . ", \$b = $b\n";
?>
Type conversion: Approach 1
<?
$dog_count = intval (strval (doubleval("101 Dalmatians")));
echo ($dog_count);
?>
Type conversion: Approach 2
<?
$dog_count = (int) (string) (double) "101 Dalmatians";
echo ($dog_count);
?>
Type conversion: approach 3
<?
$dog_count = "101 Dalmatians"
settype($dog_count, "double");
echo ($dog_count);
settype($dog_count, "string");
echo ($dog_count);
settype($dog_count, "int");
echo ($dog_count);
?>
Type conversions
<?
$type_examples[0] = 123;
$type_examples[1] = 3.14159;
$type_examples[2] = "a string";
$type_examples[3] = "9.990 (begins with number)";
$type_examples[4] = array(9,8,7);
print("<TABLE><TR>");
print("<TH>Original</<TH>");
print("<TH>(int)</<TH>");
print("<TH>(double)</<TH>");
print("<TH>(string)</<TH>");
print("<TH>(array)</<TH></TR>");
for ($index = 0; $index < 5; $index++){
print("<TR><TD>$type_examples[$index]</TD>");
$converted_var =
(int) $type_examples[$index];
print("<TD>$converted_var</TD>");
$converted_var =
(double) $type_examples[$index];
print("<TD>$converted_var</TD>");
$converted_var =
(string) $type_examples[$index];
print("<TD>$converted_var</TD>");
$converted_var =
(array) $type_examples[$index];
print("<TD>$converted_var</TD></TR>");
}
print("</TABLE>");
?>
When the first expression is a string, the type of the variable will depend on the second expression.
<?
$foo = 1 + "10.5"; // $foo is double (11.5)
$foo = 1 + "-1.3e3"; // $foo is double (-1299)
$foo = 1 + "bob-1.3e3"; // $foo is integer (1)
$foo = 1 + "bob3"; // $foo is integer (1)
$foo = 1 + "10 Small Pigs"; // $foo is integer (11)
$foo = 1 + "10 Little Piggies"; // $foo is integer (11)
$foo = "10.0 pigs " + 1; // $foo is integer (11)
$foo = "10.0 pigs " + 1.0; // $foo is double (11)
?>