Web Programming Step by Step

Lecture 7
More PHP; File I/O

Reading: 5.2, 5.4

Except where otherwise noted, the contents of this presentation are Copyright 2010 Marty Stepp and Jessica Miller.

PHP syntax template

HTML content

	<?php
		PHP code
	?>

HTML content

	<?php
		PHP code
	?>

HTML content ...

• any contents of a .php file between <?php and ?> are executed as PHP code
• all other contents are output as pure HTML
• can switch back and forth between HTML and PHP "modes"

Math operations

$a = 3;
$b = 4;
$c = sqrt(pow($a, 2) + pow($b, 2));

• the syntax for method calls, parameters, returns is the same as Java

int and float types

$a = 7 / 2;               # float: 3.5
$b = (int) $a;            # int: 3
$c = round($a);           # float: 4.0
$d = "123";               # string: "123"
$e = (int) $d;            # int: 123

• int for integers and float for reals
• division between two int values can produce a float

String type (5.2.6)

$favorite_food = "Ethiopian";
print $favorite_food[2];            # h

$favorite_food = $favorite_food . " cuisine";
print $favorite_food;               # Ethiopian cuisine

• zero-based indexing using bracket notation
• there is no char type; each letter is itself a String
• string concatenation operator is . (period), not +
  • 5 + "2 turtle doves" === 7
  • 5 . "2 turtle doves" === "52 turtle doves"
• can be specified with "" or ''

String functions

# index  0123456789012345
$name = "Stefanie Hatcher";
$length = strlen($name);              # 16
$cmp = strcmp($name, "Brian Le");     # > 0
$index = strpos($name, "e");          # 2
$first = substr($name, 9, 5);         # "Hatch"
$name = strtoupper($name);            # "STEFANIE HATCHER"

bool (Boolean) type (5.2.8)

$feels_like_summer = FALSE;
$php_is_rad = TRUE;

$student_count = 217;
$nonzero = (bool) $student_count;     # TRUE

• the following values are considered to be FALSE (all others are TRUE):
  • 0 and 0.0
  • "", "0", and NULL (includes unset variables)
  • arrays with 0 elements
• can cast to boolean using (bool)
• FALSE prints as an empty string (no output); TRUE prints as a 1

NULL

$name = "Victoria";
$name = NULL;
if (isset($name)) {
	print "This line isn't going to be reached.\n";
}

• a variable is NULL if
  • it has not been set to any value (undefined variables)
  • it has been assigned the constant NULL
  • it has been deleted using the unset function
• can test if a variable is NULL using the isset function
• NULL prints as an empty string (no output)

Arrays (5.4.3)

$name = array();                         # create
$name = array(value0, value1, ..., valueN);

$name[index]                              # get element value
$name[index] = value;                      # set element value
$name[] = value;                          # append

$a = array();     # empty array (length 0)
$a[0] = 23;       # stores 23 at index 0 (length 1)
$a2 = array("some", "strings", "in", "an", "array");
$a2[] = "Ooh!";   # add string to end (at index 5)

• to append, use bracket notation without specifying an index
• element type is not specified; can mix types

Array functions

Array function example

$tas = array("MD", "BH", "KK", "HM", "JP");
for ($i = 0; $i < count($tas); $i++) {
	$tas[$i] = strtolower($tas[$i]);
}                                 # ("md", "bh", "kk", "hm", "jp")
$morgan = array_shift($tas);      # ("bh", "kk", "hm", "jp")
array_pop($tas);                  # ("bh", "kk", "hm")
array_push($tas, "ms");           # ("bh", "kk", "hm", "ms")
array_reverse($tas);              # ("ms", "hm", "kk", "bh")
sort($tas);                       # ("bh", "hm", "kk", "ms")
$best = array_slice($tas, 1, 2);  # ("hm", "kk")

• the array in PHP replaces many other collections in Java
  • list, stack, queue, set, map, ...

The foreach loop (5.4.4)

foreach ($array as $variableName) {
	...
}

$stooges = array("Larry", "Moe", "Curly", "Shemp");
for ($i = 0; $i < count($stooges); $i++) {
	print "Moe slaps {$stooges[$i]}\n";
}
foreach ($stooges as $stooge) {
	print "Moe slaps $stooge\n";  # even himself!
}

• a convenient way to loop over each element of an array without indexes

PHP file I/O functions (5.4.5)

Reading/writing files

Hello
how r u?

I'm fine

array(
	"Hello\n",     # 0
	"how r u?\n",  # 1
	"\n",          # 2
	"I'm fine\n"   # 3
)

"Hello\n
how r u?\n      # a single
\n              # string
I'm fine\n"

• file returns lines of a file as an array (\n at end of each)
• file_get_contents returns entire contents of a file as a single string
  • file_put_contents writes a string into a file

The file function

# display lines of file as a bulleted list
$lines = file("todolist.txt");
foreach ($lines as $line) {        # for ($i = 0; $i < count($lines); $i++)
	print "<li>$line</li>\n";
}

• file returns the lines of a file as an array of strings
• each ends with \n ; to strip it, use an optional second parameter:

  $lines = file("todolist.txt", FILE_IGNORE_NEW_LINES);
  

• common idiom: foreach or for loop over lines of file

Unpacking an array: list

list($var1, ..., $varN) = array;

Marty Stepp
(206) 685-2181
570-86-7326

list($name, $phone, $ssn) = file("personal.txt");
...

• the odd list function "unpacks" an array into a set of variables you declare
• when you know a file's exact length/format, use file and list to unpack it

Reading directories

• glob can accept a general path with the * wildcard character

glob example

# reverse all poems in the poetry directory
$poems = glob("poetry/poem*.dat");
foreach ($poems as $poemfile) {
	$text = file_get_contents($poemfile);
	file_put_contents($poemfile, strrev($text));
	print "<p>I just reversed " . basename($poemfile) . "</p>\n";
}

• glob can match a "wildcard" path with the * character
  • glob("foo/bar/*.doc") returns all .doc files in the foo/bar subdirectory
  • glob("food*") returns all files whose names begin with "food"
• the basename function strips any leading directory from a file path
  • basename("foo/bar/baz.txt") returns "baz.txt"

scandir example

<ul>
	<?php
	$folder = "taxes/old";
	foreach (scandir($folder) as $filename) {
		print "<li>$filename</li>\n"
	}
	?>
</ul>

• scandir sucks; current directory (".") and parent ("..") are included in the array
• don't need basename with scandir; returns file names only without directory