02c08-1.php

来自「介绍PHP5的给类型函数应用」· PHP 代码 · 共 62 行

<?php
// An array of conversion functions to convert any unit to Kelvin
$to_K = array(
	'K' => create_function('$x', 'return $x;'),
	'C' => create_function('$x', 'return $x + 273.15;'),
	'F' => create_function('$x', 'return ($x + 459.67) / 1.8;'),
	'R' => create_function('$x', 'return $x / 1.8;') );

// And an array of conversion functions to convert Kelvin, to any unit
$from_K = array(
	'K' => create_function('$x', 'return $x;'),
	'C' => create_function('$x', 'return $x - 273.15;'),
	'F' => create_function('$x', 'return ($x * 1.8) - 459.67;'),
	'R' => create_function('$x', 'return $x * 1.8;') );

// The conversion function.  Pass it the value, the unit to convert from
// and the unit to convert to.
function convert_temp($value, $from, $to) {
	global $to_K, $from_K;
	
	// First check that we can understand the units passed to us else bail.
	if (!(isset($to_K[$from]) && isset($from_K[$to]))) {
		return false;
	} else {
		// Since we found the units all we need to do now is to convert the
		//  value to Kelvin using the provided function, then convert it 
		//  again to the desired unit.  Two function calls and we are done.
		return $from_K[$to]($to_K[$from]($value));
	}
}

// Output a Celsius <-> Fahrenheit comparison table with formatting:
?>
<style>
td, th { text-align: center; font-size: 20px; }
.extreme { border: 2px solid red; }
.hot { border: 2px solid orange; }
.comfort { border: 2px solid green; }
.cold { border: 2px solid blue; }
.freeze { border: 2px solid navy; }
</style>
<table>
 <tr><th>C</th><th>F</th></tr>
<?php
// Loop from 50 C down to -10 C, by 5's
foreach (range(50, -10, 5) as $c) {
	// Convert the temp
	$f = convert_temp($c, 'C', 'F');
	
	// Based upon known Farhenheit values, determine the range of heat:
	if ($f > 100) { $heat = 'extreme'; }
	elseif ($f > 80) { $heat = 'hot'; }
	elseif ($f > 55) { $heat = 'comfort'; }
	elseif ($f > 32) { $heat = 'cold'; }
	else { $heat = 'freeze'; }
	
	// Echo out the row of information, including formatting
	echo "<tr><td class=\"{$heat}\">{$c}</td>
<td class=\"{$heat}\">{$f}</td></tr>";		
}
?>
</table>