Making Things Talk

LOOK, MA, NO COMPUTER! 131

$readParticles = 0; // flag telling you the next line

// is the particle value

$particles = -1; // the particles value

To extract the data

you need from

those lines, you’ll need a couple more

variables. Add these lines at the top of

the program (but after the line starting

with <?php):

// if the current line contains the substring "AQI observed at"

// then the line following it is either the particle reading

// or the ozone reading:

if (preg_match('/AQI observed at /', $line)) {

// if $particles == -1, you haven't gotten

// a value for it yet:

if ($particles == -1) {

$readParticles = 1;

}

}

Then replace the command echo

$line; in the program with this block of

code:

This block uses the preg_match()

command to look for a string of text

matching a pattern you give it. In

this case, it looks for the pattern AQI

observed at. You know that when

you see that line, the next line is the

number you want. When the PHP script

finds the “observed at” line, it sets the

variable $readParticles to 1.

8

// if the previous line was the "observed at line" preceding

// the particle matter reading, then $readParticles = 1 and

// you should get this line, trim everything but the number,

// and save the result i