Introduction to PHP – Chapter 8 Working with PHP

JavaScript vs. PHP PHP scripts are similar to JavaScript scripts, but be careful with syntax! PHP variables always begin with a “$” symbol. There is no equivalent to JavaScript’s “var” data declaration. PHP scripts are embedded within a tag. PHP functions are similar to JavaScript functions, but argument passing is easier. PHP functions can “return” a single value, with multiple values returned as elements in an array. PHP scripts can read data from and write data to a file on a remote server. PHP outputs can be used within the PHP application, but not “passed back” to JavaScript.

Solving the Water Vapor Problem Pass instrument serial number, time and place, and instrument output voltages. Find calibration constants for the instrument. Calculate sun’s position based on time and place (long!). Calculate total column water vapor (short). Where should the solar position calculations be done (they depend on time and place, but are independent of the instrument outputs)?

Decisions, decisions… Solar position calculations could be done in JavaScript, but we will do them in PHP to learn how to use the language. Document 8.1 gives a complete JavaScript solution, assuming that the instrument calibration constants area known. Eventually, these calculations need to be translated into PHP.

A self-contained JavaScript solution

JavaScript… function getSunpos(m,d,y,hour,minute,second,Lat,Lon) { with (Math) { // Explicit type conversions to make sure inputs are treated like numbers, not strings. m=parseInt(m,10); d=parseInt(d,10); y=parseInt(y,10); hour=parseFloat(hour); minute=parseFloat(minute); second=parseFloat(second); Lat=parseFloat(Lat); Lon=parseFloat(Lon); Note the use of parseFloat() and parseInt() to convert form field values to numbers. function get_PW(IR1,IR2,A,B,C,beta,tau,airm,p) { var x = C*airm*tau - (Math.log(IR2/IR1)-A)/B; var PW = Math.pow(x,1./beta)/airm; return Math.round(PW*1000.)/1000.; }

PHP equivalent… $m=getSunpos($_POST["mon"],$_POST["day"],$_POST["yr"],$_POST["hr"], $_POST["min"],$_POST["sec"], $_POST["lat"],$_POST["lon"]); $x = $C*$m*$tau - (log($IR2/$IR1)-$A)/$B; $PW = pow($x,1./$beta)/$m;

An HTML interface to PHP

Output from PHP

Returning multiple values Document 8.4. (circleStuff.php) <?php /* Note that this: function CIRCLESTUFF($r) { will also work because PHP function names are case-insensitive! */ function CircleStuff($r) { $area=M_PI*$r*$r; $circumference=2*M_PI*$r; /* However, this won't work: return array($AREA,$circumference); because variable names are case-sensitive. */ return array($area,$circumference); } list($area,$circumference) = CircleStuff(3); echo $area. ", ". $circumference; ?>

More about file I/O A text file contains wind speed data: , 0.4, 3.8, 4.5, 3.3, 1.9, 1.6, 3.7, 0.8, 2.3, 2.8, 2.4, 2.5, 3.2, 4.1, 3.9, 5.0, 4.4, 4.4, 5.5, 3.0, 3.7, 2.2, , 2.8, 2.3, 2.3, 1.2, 2.4, 3.1, 4.0, 3.6, 2.9, 6.0, 4.4, 0.8, 3.8, 3.5, 4.5, 2.7, 3.4, 6.6, 5.2, 1.6, 1.2, 2.3, 2.4 … , 5.9, 3.1, 3.2, 4.5, 4.4, 3.9, 4.4, 7.5, 8.4,10.2, 9.2, 8.1, 6.3, 3.1, 3.5, 2.2, 1.4, 0.4, 4.2, 5.4, 4.0, 2.9, , 2.3, 2.1, 1.5, 2.3, 4.1, 5.3, 6.0, 6.0, 9.7,11.3,12.7,13.0,13.0,11.6, 9.9, 9.6, 8.7, 5.4, 5.1, 5.3, 5.6, 4.4, 4.2 … For each day, there are 24 hourly wind speed values. Missing hours are represented by a value of -1. Read this file and count and display the month (1-12) and the number of missing values for each month. Write the results into a file and save it.

Document 8.4. (windspd.php) <?php $inFile="windspd.dat"; $outFile="windspd.out"; $in = fopen($inFile, "r") or die("Can't open file."); $out=fopen("c:/Documents and Settings/ All Users/Documents/phpout/".$outFile,"w"); while (!feof($in)) { // Read one month, year, # of days. fscanf($in,"%u %u %u",$m,$y,$nDays); if (feof($in)) exit; echo $m. ', '. $y. ', '. $nDays. ' '; $nMissing=0; for ($i=1; $i<=$nDays; $i++) { $hrly = fscanf($in, "%f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f, %f"); for ($hr=0; $hr '; } echo 'Number of missing hours this month is '. $nMissing. '. '; fprintf($out,"%u, %u, %u\r\n",$m,$y,$nMissing); } fclose($in); fclose($out); ?>

Another application Write an HTML document that allows a user to select a solid object shape and enter its dimensions and the material from which it is made. The choices could be a cube, a rectangular block, a sphere, or a cube. You could choose a number of possible materials—air, gold, water, etc. Then call a PHP application that will find the mass of the object by calculating its volume based on the specified shape and looking up the density of the material in a data file.

Document 8.5a (getMass.htm) Calculate mass Enter length: Enter width: Enter height: Enter radius: cube cylinder rectangular block sphere air aluminum gold oxygen silver water <input type="submit" value="Click to get volume." <!-- <input type="button" value="click" onclick="alert(document.form1.shapes.selectedIndex); alert(shapes.options[shapes.selectedIndex].value); " --> />

PHP, the first step… This code will display something like this: Array ( [L] => 1 [W] => 1 [H] => 1 [R] => 3 [shapes] => cube [material] => oxygen ) Display the input values…

Create data files… (volume.dat) shape volume cube $L*$L*$L sphere 4/3*M_PI*$R*$R*$R cylinder M_PI*$R*$R*$L block $L*$W*$H (density.dat) material density (kg/m^3) water 1000 aluminum 2700 gold silver oxygen air 1.2

Find the material… Document 8.5b (getMass.php) ". $material. ", ". $shape. " "; $materialFile=fopen("density.dat","r"); $shapeFile=fopen("volume.dat","r"); // Read materials file. $found=false; $line=fgets($materialFile); while ((!feof($materialFile)) && (!$found)) { $values=fscanf($materialFile,"%s %f",$m,$d); if (strcasecmp($material,$m) == 0) { echo $material. ", ". $m. ", ". $d. " "; $found=true; } }

Calculate the volume… // Read volume file. $found=false; $line=fgets($shapeFile); while ((!feof($shapeFile)) && (!$found)) { $values=fscanf($shapeFile,"%s %s",$s,$v); if (strcasecmp($shape,$s) == 0) { echo $shape. ", ". $v. " "; $found=true; } } // Close both data files. fclose($materialFile); fclose($shapeFile); // Calculate mass. $vv=$v. "*$d"; echo "Result: ".eval("return round($vv,3);")." kg "; ?> This is the clever code!

Self-contained HTML/PHP applications Document 8.11 (CompoundInterest.php) Calculate Compound Interest Calculate Compound Interest " method="post"> Initial amount (no commas), $: <input type="text" name="initial" value="10000" /> Annual interest rate, %: <input type="text" name="rate" value="4" /> How many years?: <input type="text" name="years" value="20" /> <input type="submit" value="Generate compound interest table." /> "; for ($i=1; $i "; } ?>