1 Introduction to PHP Part #2
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1
Introduction to PHPPart #2
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Simple PHP Script
• Consider the following HTML file, example.html:
<html><head><title>My Page</title></head><body>Hello world!<p></body></html>
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Simple PHP Script• Here is an equivalent PHP script. PHP files have the extension “.php” and may
contain both HTML and PHP code, which is enclosed inside <? code ?> tags, or alternately <?php code ?>
<html><head><title>My Page</title></head><body><? print(“hello world!<p>”); ?></body></html>
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Simple PHP Script
• More interesting version, displays the date as known by the server:
<html><head><title>My Page</title></head><body><? print(“hello world! Timestamp: “ . time() . “<p>”); ?></body></html>
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PHP Time Stamp
• The “.” is used to concatenate strings
• The server parses the document and interprets code within the <? ?> tags instead of sending it directly to the client– i.e. you can write code to output the HTML you
desire
• Output of previous:
hello world! Timestamp: 1050289182
hello world! Timestamp: 1050289184Refresh twoSeconds later:
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PHP Script• Often everything is placed inside the PHP tags.
The following is equivalent; the header function specifies the MIME Type; i.e. that the document is HTML (as opposed to graphics, etc.):
<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); print("hello world! Timestamp: " . time() . "<p>"); print("</BODY></HTML>");?>
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Identifiers and Data Types
• Identifiers– Case-sensitive– Same rules as Java
• Data Types– integer– double– string, surrounded by “ “ or by ‘ ‘
– Weak typing; you do not declare variables, just use them and the value assigned is the type of the variable; any old value is gone
– Can typecast just like Java• (int), (double), (string), etc.
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Variables
• A variable is an identifier prefaced by $• Example:
$x = 1; $y = 3.4; $z = $x + $y; $a = true; $s = "hello!"; print ($z . " " . $a . " " . $s);
Output: 4.4 1 hello! Note: true = non zero or not empty. False = 0 or the empty string “”
Common novice mistake: Forgetting the $
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Variables
• Interpreted; consider the following: $x = 1; $y = “x”; print($y);
Output: 1
• Often {} are used to denote variable boundaries:$x = 1;$y = “x”;print({$y});
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Form Variables
• If an HTML form invokes a PHP script, the PHP script can access all of the form variables by name
• Invoking FORM:<form method=post action=“scr.php”><input type=text name=“foo” value=“bar”>
<input type=submit value=“Submit”></form>
• Inside scr.php:print($_REQUEST['foo']); // Outputs “bar”
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Sample PHP Form<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); print("foo = " . $_REQUEST[‘foo’] . ", bar = " . $_REQUEST[‘bar’] . "<P>"); print("<form method=post action=\"example.php\">"); print("<input type=text name=\"foo\" value=\"zot\">"); print("<input type=hidden name=\"bar\" value=3>"); print("<input type=submit>"); print("</form>"); print("</BODY></HTML>");?>
Note: \” escape characterCould also use ‘ instead
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Sample PHP Form
• First load:
• Upon submit:
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Web browser
• What the web browser receives after the first load. Note that we see no PHP code:
<HTML><HEAD><TITLE>My Page</TITLE></HEAD><BODY>foo = , bar = <P><form method=post action="example.php"><input type=text name="foo" value="zot"><input type=hidden name="bar" value=3><input type=submit></form></BODY></HTML>
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GET and POST• One way to hide the printing of variables when the
code is first loaded is to detect if the program is invoked via GET or POST
<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); if ($_SERVER['REQUEST_METHOD'] == ‘POST') { print("foo = " . $_REQUEST[‘foo’] . ", bar = " . $_REQUEST[‘bar’] . "<P>"); } print("<form method=post action=\"example.php\">"); print("<input type=text name=\"foo\" value=\"zot\">"); print("<input type=hidden name=\"bar\" value=3>"); print("<input type=submit>"); print("</form>"); print("</BODY></HTML>");?>
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Operators
• Same operators available as in Java:+, -, *, /, %, ++, -- (both pre/post)
+=, -=, *=, etc.
<, >, <=, >=, ==, !=, &&, ||, XOR, !
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Assignments
• PHP will convert types for you to make assignments work
• Examples:print(1 + "2"); // 3
print("3x" + 10.5); // 13.5
$s = "hello" . 55;
print("$s<p>"); // hello55
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Arrays
• Arrays in PHP are more like hash tables, i.e. associative arrays– The key doesn’t have to be an integer
• 1D arrays– Use [] to access each element, starting at 0– Ex:
$arr[0] = “hello”;$arr[1] = “there”;$arr[2] = “zot”;$i=0;print(“$arr[$i] whats up!<p>”); // Outputs : hello whats up!
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Arrays
• Often we just want to add data to the end of the array, we can do so by entering nothing in the brackets:
$arr[] = “hello”;
$arr[] = “there”;
$arr[] = “zot”;
print(“$arr[2]!<p>”); // Outputs : zot!
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Array Functions
• There are many array functions; here are just a few:
count($arr); // Returns # items in the arraysort($arr); // Sorts arrayarray_unique($arr); // Returns $arr without duplicates
print_r($var); // Prints contents of a variable // useful for outputting an entire
array // as HTML
in_array($val, $arr) // Returns true if $val in $arr
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Multi-Dimensional Arrays
• To make multi-dimensional arrays just add more brackets:
$arr[0][0]=1;
$arr[0][1]=2;
$arr[1][0]=3;
..etc.
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Arrays with Strings as Key
• So far we’ve only seen arrays used with integers as the index• PHP also allows us to use strings as the index, making the
array more like a hash table• Example:
$fat[“big mac”] = 34;$fat[“quarter pounder”]=48;$fat[“filet o fish”]=26;$fat[“large fries”]=26;print(“Large fries have “ . $fat[“large fries”] . “ grams of fat.”);
// Output : Large fries have 26 grams of fat
Source: www.mcdonalds.com
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Iterating through Arrays with foreach
• PHP provides an easy way to iterate over an array with the foreach clause:
• Format: foreach ($arr as $key=>$value) { … }
• Previous example:
foreach($fat as $key=>$value)
{
print(“$key has $value grams of fat.<p>”);
}
Output:
big mac has 34 grams of fat. quarter pounder has 48 grams of fat. filet o fish has 26 grams of fat. large fries has 26 grams of fat.
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Foreach
• Can use foreach on integers too:
$arr[]="foo"; $arr[]="bar"; $arr[]="zot"; foreach ($arr as $key=>$value) { print("at $key the value is $value<br>"); }
Output: at 0 the value is fooat 1 the value is barat 2 the value is zot
If only want the value,can ignore the $key variable
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Control Statements
• In addition to foreach, we have available our typical control statements
– If– While– Break/continue – Do-while– For loop
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IF statement
• Format:
if (expression1){
// Executed if expression1 true}elseif (expression2){
// Executed if expression1 false expresson2 true}…else{
// Executed if above expressions false}
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While Loop
• Format:
while (expression)
{
// executed as long as expression true
}
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Do-While
• Format:
do
{
// executed as long as expression true
// always executed at least once
}
while (expression);
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For Loop
• Format:
for (initialization; expression; increment)
{
// Executed as long as expression true
}
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Control Example
srand(time()); // Seed random # generator with time
for ($i=0; $i<100; $i++) { $arr[]=rand(0,10); // Random number 0-10, inclusive } $i=0; while ($i<=10) { // Initialize array of counters to 0 $count[$i++]=0; } // Count the number of times we see each value foreach ($arr as $key=>$value) { $count[$value]++; } // Output results foreach ($count as $key=>$value) { print("$key appeared $value times.<br>"); }
Counts # of random numbers generated between 0-10
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Output
0 appeared 9 times.1 appeared 9 times.2 appeared 11 times.3 appeared 14 times.4 appeared 6 times.5 appeared 7 times.6 appeared 8 times.7 appeared 11 times.8 appeared 5 times.9 appeared 9 times.10 appeared 11 times.
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Functions
• To declare a function:
function function_name(arg1, arg2, …) {
// Code// Optional: return (value);
}
Unlike most languages, no need for a return type since PHP is weakly typed
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Function Example: Factorial
function fact($n)
{
if ($n <= 1) return 1;
return ($n * fact($n-1));
}
print(fact(5)); // Outputs 120
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Scoping
• Variables defined in a function are local to that function only and by default variables are pass by value
function foo($x,$y){ $z=1; $x=$y + $z; print($x); // Outputs 21}
$x=10;$y=20;foo($x,$y);print(“$x $y<p>”); // Outputs 10 20
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Arrays: Also Pass By Valuefunction foo($x){ $x[0]=10;
print_r($x); Array ( [0] => 10 [1] => 2 [2] => 3 ) print("<p>");}
$x[0]=1; $x[1]=2; $x[2]=3;
print_r($x); Array ( [0] => 1 [1] => 2 [2] => 3 ) print("<p>"); foo($x);
print_r($x); Array ( [0] => 1 [1] => 2 [2] => 3 ) print("<p>"); Not changed!
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Pass by Reference
• To pass a parameter by reference, use & in the parameter list
function foo(&$x,$y){ $z=1; $x=$y + $z; print($x); // Outputs 21}
$x=10;$y=20;foo($x,$y);print(“$x $y<p>”); // Outputs 21 20
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Dynamic Functions
• Functions can be invoked dynamically too
• Useful for passing a function as an argument to be invoked later
function foo() { print("Hi<p>"); }
$x="foo"; $x(); // Outputs “Hi”
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Classes & Objects
• PHP supports classes and inheritance• All instance variables are public in PHP 4 (PHP 5 allows private,
protected)• Format for defining a class; the extends portion is optional
class name extends base-class{
var varName;…function name() {… constructor code …}function methodName() { … code … }
…}
• To access a variable or function, use $obj->var (no $ in front of the var)• To access instance variables inside the class, use $this->var
needed to differentiate between member var and a new local var
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Class Example class user { var $name; var $password; function user($n, $p) { $this->name=$n; $this->password=$p; } function getSalary() { // if this was real, we might // look this up in a database or something return 50000; } }
$joe = new user("Joe Schmo","secret"); print($joe->name . " - " . $joe->password . "<p>"); print($joe->getSalary() . "<p>");
Output:
Joe Schmo - secret
50000
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Objects in PHP 4
• Assigning an object makes a new copy, not a reference like Java:
$joe = new user("Joe Schmo","secret"); $fred = $joe; $joe->password = "a4j1%"; print_r($joe); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>"); print_r($fred); // user Object ( [name] => Joe Schmo [password] => secret ) print("<p>");
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Objects in PHP 5
• Assigning an object makes a reference to the existing object, like Java:
$joe = new user("Joe Schmo","secret"); $fred = $joe; $joe->password = "a4j1%"; print_r($joe); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>"); print_r($fred); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>");
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Other new items in PHP 5
• Mostly improvements in OOP model– Abstract classes and methods– Destructors– Cloning– instanceof– Reflection
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Using PHP
• Here we will focus on additional functions that will be helpful for you to complete the homework assignment
– Type Checking• is_array, is_string, is_long, is_double
– Useful string functions• strlen, implode, explode, substr, strstr, trim, char access
– File I/O• fopen, fread, feof, fclose, fwrite
– Some examples
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Type Checking
• PHP includes several functions to determine the type of a variable since it may not be obvious what the type is due to conversions
is_int($x) // returns true if $x is an integer
is_double($x) // returns true if $x is a double
is_array($x) // returns true if $x is an array
is_string($x) // returns true if $x is a string
is_null($x) // returns true if $x is a null
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String Functions
• We can access a string as an array to retrieve individual characters:
$s=“hithere”;$z = $s[0] . $s[2] . $s[4];print($z); // hte
• We can also assign characters to the string:$s[2] = “F”;print($s); // hiFhere
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Strings
• String length: strlen($s) returns the length of the string
$s="eat big macs"; for ($i=0; $i<(strlen($s)-1)/2; $i++) { $temp = $s[$i]; $s[$i] = $s[strlen($s)-$i-1]; $s[strlen($s)-$i-1] = $temp; }
print($s); // Output : scam gib tae
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Strings
• Substring: Searches a string for a substringPrototype:
string strstr (string haystack, string needle)• Returns all of haystack from the first occurrence of needle to
the end. • If needle is not found, returns FALSE.
$email = ‘[email protected]'; $domain = strstr ($email, '@');
print ($domain); // prints @acm.org
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Strings
• strtolower($s) : returns $s in lowercase$s=“AbC”;$s = strtolower($s); // $s = “abc”
• strtoupper($s) : returns $s in uppercase$s = “AbC”;$s = strtoupper($s); // $s = “ABC”
• trim($s) : returns $s with leading, trailing whitespace removed
$s = “ \n ABC \r\n”; $s = trim($s); // $s = “ABC”
Trim is useful to remove CR’s and Newlines when reading lines of data from text files or as input from a form (e.g. textbox, textarea)
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Strings
• Substring: Format:string substr (string string, int start [, int length])– Substr returns the portion of string specified by the start and length parameters.
– If start is positive, the returned string will start at the start'th position in string, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.
• Examples:$rest = substr ("abcdef", 1); // returns "bcdef" $rest = substr ("abcdef", 1, 3); // returns "bcd"
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Implode
• Implode is used to concatenate elements of an array into a single string
string implode (string glue, array pieces)• Returns a string containing a string representation of all the
array elements in the same order, with the glue string between each element.
• Examples$arr[]="A"; $arr[]="B"; $arr[]="C";$s = implode(",",$arr); // $s = “A,B,C”$s = implode("",$arr); // $s = “ABC”
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Explode
• Explode is used to create an array out of a string with some delimiter
array explode (string separator, string string)• Returns an array of strings, each of which is a substring of string
formed by splitting it on boundaries formed by the string separator.
• Example$s="eat:large:fries";$arr = explode(":",$s);print_r($arr);print("<p>");
Output: Array ( [0] => eat [1] => large [2] => fries )
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File I/O• Opening a file: fopen• Format:
int fopen (string filename, string mode)– Filename is the complete path to the file to open; must have proper
permissions– Mode is one of the following
• 'r' - Open for reading only; place the file pointer at the beginning of the file. • 'r+' - Open for reading and writing; place the file pointer at the beginning of the
file. • 'w' - Open for writing only; place the file pointer at the beginning of the file and
truncate the file to zero length. If the file does not exist, attempt to create it. • 'w+' - Open for reading and writing; place the file pointer at the beginning of
the file and truncate the file to zero length. If the file does not exist, attempt to create it.
• 'a' - Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
• 'a+' - Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.
– Returns: a file pointer used to reference the open file
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File I/O
• Reading from a text file:string fgets (int filepointer, int length)
– Returns a string of up to length - 1 bytes read from the file pointed to by fp.
– Reading ends when length - 1 bytes have been read, on a newline (which is included in the return value), or on EOF (whichever comes first).
– We can use this function on files we have opened for reading
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File I/O
• Writing to a text file:int fwrite (int fp, string string)– fwrite() writes the contents of string to the file stream pointed to
by fp. – The file must be opened for writing
• Checking for end of filefeof(int fp)Returns true if we have reached the end, false otherwise
• Closing a filefclose(int fp)Use when done with the file and close the file pointer
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File I/O example
$fd = fopen ("/proc/cpuinfo", "r");
while (!feof ($fd)) {
$oneline = fgets($fd, 4096);
print("$oneline<br>");
}
fclose ($fd);
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fgets
• IMPORTANT – Remember that fgets returns the string WITH the newline
• This is critical if you are going to perform comparisons– You’ll get a false match if the newline is not
accounted for– Easiest technique: trim out the newlines
$oneline = trim(fgets($fp, 1024));
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Example
• Create a single PHP script that generates a form with a textarea– Allow the user to enter numbers in the textarea– Submit the form to the same script– Compute the sum of the numbers in the textarea
and print it out
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Example.php
<?phpheader("Content-Type: text/html");print("<HTML><HEAD><TITLE>My Page</TITLE>");
print("</HEAD>");print("<BODY>");
if($_SERVER['REQUEST_METHOD'] != "POST"){
// We are loading for the first time,// not receiving a form. So generate// a form allowing the user to enter// data in a text area and have it submitted// to this same scriptprint("<FORM method=post action='example.php'>");print("Enter numbers below.<p>");print("<TEXTAREA name='myData' rows=10></TEXTAREA>");print("<INPUT type=submit>");print("</FORM>");
}
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Example.phpelse{
// We are receiving data from our form// Put the text data into an array. Each// is separated by a newline, so use explode// to parse$a = explode("\n",$_REQUEST['myData']);// Here we loop through and add up the numbers$total = 0;foreach ($a as $key=>$value) {
// Each element in the array is a string,// but note that each will contain a \r// whitespace at the end, so you may wish// to trim these out. It is not really// necessary in this example but you will// probably want to trim for your homework$num = (int) trim($value);$total += $num;
}print("The sum of your numbers is $total<p>");
} print("</BODY></HTML>");?>
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Execution
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Summary
• PHP is an imperative language for the web• Similarities to C, Java, and even interpreted
languages• Can’t do everything since server side only –
sometimes coupled with client-side languages such as JavaScript
• PHP version 5 not quite backward compatible with PHP 4
• Easy to write sloppy code so one must be more disciplined in design of classes, functions, variables, HTML, documentation
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Lots More to PHP• We have only scratched the surface, but there is much more that
PHP can do– Generate graphics (gd library)– Networking, Sockets, IRC, Email– Database Access – LDAP– Regular Expressions– PDF– Java– XML– Design methodologies (e.g. FuseBox, include files)– Many more
• See the excellent resources online– www.php.net– www.phpbuilder.com– www.zend.com
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End of PHP
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