Chapter 2: PHP Language (I)

Chapter 2: PHP Language (I)

Overview • Introduction • Getting Start • Writing PHP • Variables & Constants • Data Types • Operators • Flow control • Functions

Introduction • PHP: Hypertext Preprocessor • A widely-used Open Source general-purpose scripting language. • Originally designed to create dynamic web pages, PHP's principal focus is server-side scripting. • PHP scripts can be embedded into HTML. • The LAMP architecture has become popular in the Web industry as a way of deploying inexpensive, reliable, scalable, secure web applications. • PHP is commonly used as the P in this bundle alongside Linux, Apache and MySQL. • FAMP replaces Linux with FreeBSD, WAMP replaces Linux with Windows. • Key Point: • Server-side, scripting language.

Getting Start (1) • Put the php code into your html documents. • Generally, the PHP code is embedded in html tags. • These special tags are <? ……… ?> <?php ……… ?> • You can also make it using “<script>” tag <script language=“php”> …… …… </script> • Generally the filename ends with “.php”, “.php5”, or “.phtml”

Getting Start (2) • Example: <html> <head><title> Welcome to PHP Pages</title></head> <body> <?php for( $i = 1 ; $i <= 4 ; $i++){ echo "Font Size: $i - "; echo "Welcome Using PHP Language \n"; } ?> </body> </html>

PHP Server Web Pageswith PHP Code HTML Docs Getting Start (3) • Server-side processing • Viewing the Output: [檢視]  [檢視原始檔] <html> <head><title> Welcome to PHP Pages</title></head> <body> Font Size: 1 - Welcome Using PHP Language Font Size: 2 - Welcome Using PHP Language Font Size: 3 - Welcome Using PHP Language Font Size: 4 - Welcome Using PHP Language </body> </html> <html> <head><title> Welcome to PHP Pages</title></head> <body> <?php for( $i = 1 ; $i <= 4 ; $i++){ echo "Font Size: $i - "; echo "Welcome Using PHP Language \n"; } ?> </body> </html>

Getting Start (3) • Practicing • Writing Your PHP “Hello World” <html> <head><title> Hello World to PHP Pages</title></head> <body> <?php echo "Hello World"; ?> </body> </html>

Writing PHP (1) • PHP Example • “;” – end of statements • “//” – comment line • /* ……… */ – comment several lines <?php // for loop for( $i = 1 ; $i <= 4 ; $i++) { /* * display different font-size welcome messages */ echo "Font Size: $i - "; echo "Welcome \n"; } ?>

Writing PHP (1) • PHP Example • “.” – string concatenation <html> <head><title> Hello World to PHP Pages</title></head> <body> <?php echo "Welcome Using"." PHP Language"; ?> </body> </html>

Writing PHP (2) • Practicing • Writing a PHP program to show welcome message. • Using strings concatenation your welcome message. • Adding some comment to explain what to do? <html> <head><title>Hello World to PHP Pages</title></head> <body> <?php // say hello world echo "Hello"." World"; ?> </body> </html>

Variables & Constants (1) • Variables • To store some data in program execution • Need no declaration in php. • Naming of Variables • Starting with alphabets (a-zA-Z) or underline (“_”) • After that, alphabets, numbers, and underlines are allowed, without length constrains. • Ex. – N, n, size, a10, short_v1, _help, _4tmp, Count ※Note: variable names are case sensitive. • ‘Hello’ is different with ‘hEllo’ • Indicating Variables • Adding ‘$’ in front of variable name • Ex. – $N, $n, $size, $a10, $short_v1, $_help, $_4tmp, $Count

Variables & Constants (2) • Value Assignment • By Value $name = “Tsung-Hsi Weng”; // string $score = 80; // integer $id = “1230017”; // string • By Variable $nickname = $name; // copy values in $name into $nickname // $nickname will not change with $name • By Reference $sid = &$id; // reference assignment (like pointer in C) // $sid will be changed while changing $id ※Data type of one variable changes with what it is assigned. $x = 85; // $x is integer here. $x = “127”; // now, $x is a string.

Variables & Constants (3) • Outputting Variable in PHP • Language Constructs: echo(), print() • To output something you want to. • Not actually real functions. • Can be used with or without “()”. • Difference between echo & print: • Variables in echo can be separated with “,”; echo “Hello World \n”; echo “Hello ” . “World” . “ \n”; echo “Hello ” , “World” , “ \n”; • Simplified written <? echo $var ?> <?=$var ?>

Variables & Constants (4) • Practicing • Adding some variables in your php to store your personal information, and printout the variable result. • Changes value in them, and printout it again. <html> <head><title>Hello</title></head> <body> <?php $name = "Peter"; $lang = "PHP"; echo "Hello. My name is $name. "; echo "This page is produced by $lang. "; $name = "Bill"; echo "$name is my friend."; ?> </body> </html>

Variables & Constants (5) • Dynamic Variable • “Dynamic Variable” is easy to be implemented in interpreted languages. • PHP: Variable Variable Name <html> <head> <title> Dynamic Variable In PHP </title> </head> <body> <?php $a="b"; $b="c"; $c="d"; echo '$a=', $a, " \n"; // $a=b echo '$$a=', $$a, " \n"; // $$a=c echo '$$$a=', $$$a, " \n"; // $$$a=d ?> </body> </html>

Variables & Constants (6) • Constants • Naming: similar to variables • Indicating: just use the name of constants • Also case sensitive • Defining a constant • Syntax: define (“CONSTNAME”, VALUE); define (“PI”, 3.1415926); define (“TEACHER”, “Tsung-Hsi Weng”); • Predefined constants

Variables & Constants (7) • Example <html> <head> <title>Constants In PHP </title> </head> <body> <?php define ("PI", 3.1415926); echo "This line number before 'PI' is ".__LINE__." "; echo "PI is ".PI.". "; echo "This line number after 'PI' is ".__LINE__; ?> </body> </html>

Data Types (1) • 8 basic data types • boolean, integer, float, string , NULL, array, object, resource • Boolean • True / False • Case insensitive (TRUE = True) • Usually used in logical operation. • $percentage>=0.5 will be true or false. • Integer • Range: -2147483648 ~ 2147483647 (32 bits) • Expression • Decimal: 5678, -1234 • Octal: 0234, -0135 • Hexadecimal: 0x1A, -0x3fc • Floating Point Number (float) • Range: 4.94065645841246544e-324 ~ 1.79769313486231570e308 (64 bits) • Ex. 2.345, 1.2e3 (=1200), 7E-4 (=0.0007)

Data Types (2) • String • Characters connected, quoted with ‘’ or “” • Ex. ‘This is a string’, “This is a string, too.” • Difference between single quote (‘’) and double quote (“”) • Double quote will do variable exchange, but single quote do not. $user = “chwong”; echo "$user"; // output chwong echo '$user'; // output $user • Escape characters – \ \n – LF, Line Feed. (New Line) \r – CR, Carriage Return. (ENTER) \t – TAB \\ –「\」 \$ –「$」 \” –「”」 \’ –「’」

Data Types (3) • NULL • Only one value: NULL • Case insensitive (NULL = null) • Cases • Undefined variables • Variables assigned to NULL • Variable unsetted. (using unset() ) • Array, Object, Resource • Not mentioned here.

Data Types (4) • Practicing • Adding three integer variables and assigning to 100 with three different expressions, and printout individual result. • Adding three float variables and assigning to 314.16 with three different expressions, and printout individual result. <?php $int1 = 100; $int2 = 0x64; $int3 = 0144; $str1 = "int1 = $int1, int2 = $int2, int3 = $int3 "; $ft1 = 314.16; $ft2 = 3.1416e2; $ft3 = 31416E-2; $str2 = "ft1 = $ft1, ft2 = $ft2, ft3 = $ft3”; echo "$str1 $str2"; ?>

Data Types (5) • Type Conversions • Automatically • Operations with different types of operands. • Example • Cast Operator • Syntax: (data type) expression or variable • Example $a=17; $b=5; $c = (int) ($a / $b); // $c=3 echo (string) $a . (string) $b; // output 175

Data Types (6) • Practicing • Adding variable pi and assigning string value “3.146” and compute circle area with radius equal 3 unit. Finally printout the result used integer. • Using cast operator. <html> <head> <title>Conversion Data Type</title> </head> <body> <?php $pi = "3.1416"; $radius = 3; $area = $pi * ($radius * $radius); echo "Radius = $radius, Circle area is ",(int)$area; ?> </body> </html>

Operators (1) • Types of operators • Arithmetic, Comparison, Logical, Bitwise, Combined Operators, String Concatenation, Error Control • Priorities • Ex: <html> <head> <title>Conversion Data Type</title> </head> <body> <?php echo 2 * 3 + 1 * (1 + 6 / 2); //10 ?> </body> </html>

Operators (2) • Arithmetic ( + - * / % ++ --) • Ex. $a=5; $b=4; $c = -$a; // $c = -5 $c = $a + $b; // $c = 9 $c = $a - $b; // $c = 1 $c = $a * $b; // $c = 20 $c = $a / $b; // $c = 1.25 $c = $a % $b; // $c = 1 echo $a++; // output 5, $a = 6 echo ++$b; // $b = 5, output 5 $b--; // $b = 4

Operators (3) • Comparison ( > < == >= <= === != ) • Results: True / False • Ex. $a = 123; $b = "456"; $c = $a > $b; echo $c; // False, display NULL string $c = $a < $b; echo $c; // True, display 1 $c = $a === $b; echo $c; // False, display NULL string $c = ($a = $b) == $b; echo $c; // True, display 1 $c = $a < $b; echo $c; // False, display NULL string $c = $a <= $b; echo $c; // True, display 1 $c = $a >= $b; echo $c; // True, display 1 $c = $a != $b; echo $c; // False, display NULL string $c = $a === $b; echo $c; // True, display 1

Operators (4) • Logical ( && || ! and or xor) • Results: True / False • Ex. $a = 123; $b = "456"; $c = $a < 100 && $b > 400; // $c = false $c = $a == 123 && $b == 456; // $c = true $c = $a > 200 || $b > 200; // $c = true // and/or/xor priority is higher then assign operator (=) $c = $a > 200 or $b > 200; // $c = false $c = $a == 456 and $b == 456; // $c = false $c = !($a == 456) and $b == 456; // $c = true $c = !($a == 456) xor $b == 456; // $c = true $c = ($a < 100 xor $b > 400); // $c = true $c = ($a > 100 xor $b > 400); // $c = false

Operators (5) • Bitwise ( ~ & | ^ << >>) • Ex. $a = 1; $a = 192 & 0x80; // $a = 128; $a = 192 & ~0x80; // $a = 64; $a = 1 | 3 | 4; // $a = 7; $a = 1 << 2; // $a = 4; $a = -1 << 2; // $a = -4; $a = 256 >> 2; // $a = 64; $a = -256 >> 2; // $a = -64;

Operators (6) • Combined ( += -+ *= /= %= .= <<= >>= &= |= ^=) • Ex. $a=5; $b=4; $a += $b; // $a = 9 $a *= $b; // $a = 36 $a -= $b; // $a = 32 $a /= $b; // $a = 8 $a %= $b; // $a = 0 $a .= $b; // $a = “04” $a <<= 2; // $a = 16 $a >>= 1; // $a = 8 $a |= 3; // $a = 11 $a ^= 12; // $a = 7 $a &= 4; // $a = 4

Operators (7) • String Concatenation ( . ) • Ex. <html> <head><title> Hello World to PHP Pages</title></head> <body> <?php echo "Welcome Using"." PHP Language"; ?> </body> </html>

Operators (8) • Error Control ( @ ) • Ex. echo ( 5 / 2 ), "\n"; // output 2.5 echo ( 5 / 0 ), "\n"; // Warning: Division by zero in filename on line # echo @ ( 5 / 2 ), "\n"; // output 2.5 echo @ ( 5 / 0 ), "\n"; // output nothing

Flow Control (1) • Flow Controls • Conditional • if … elseif … else … • switch … case … default… • ?: • Loop • for loop • foreach loop • while loop • do/while loop • require/require_once • include/include_once

Code before false condition true Code in if-block Code after Flow Control (2) • Conditional • if code before; if ( condition ) { code in if-block; } code after; • Example if ( $score < 60 ) { echo “You cannot pass!”; }

Code before true false condition Code inif-block Code inelse-block Code after Flow Control (3) • if … else code before; if ( condition ) { code in if-block; }else { code in else-block; } code after; • Example if ( $score < 60 ) { echo “You cannot pass!”; } else { echo “Congratulations!”; }

Flow Control (4) • ?: – ternary operator condition ? expression1 : expression2; • Same as if (condition) { expression1 } else { expression2 } • Example echo $score < 60 ? "You cannot pass!" : "Congratulations!";

Code before true false condition true false condition2 Code inif-block Code inelseif-block Code inelse-block Code after Flow Control (5) • if … elseif … else code before; if ( condition ) { code in if-block; }elseif (condition2) { code in elseif-block; }else { code in else-block; } code after; • Example repeatable if ( $score > 90 ) { echo “You are so great!”; } elseif ( $score > 60 ) { echo “Nice grade.”; } else { echo “You cannot pass!”; }

Flow Control (6) • switch-case switch ( variable ) { case value1: code when value1; break; case value2: code when value1; break; default: code when other; }

Flow Control (7) • Example Switch ( $option ) { case 1: echo “You select option 1”; break; case 2: echo “You select option 2”; break; default : echo “I don’t what did you select”; break; }

Flow Control (8) • Practicing • Adding a variable which store 0~6 is individual mean Sunday to Saturday, printout the variable which mean. • Using one of switch-case or if-else in php. <?php $day = 3; switch ($day) { case 0: echo "Sunday"; break; ... ... case 6: echo "Saturday"; break; default: echo "what day is today?"; } ?>

Flow Control (9) • Loops • for loop for (initial expression; condition expression; end expression) { statements } • The initial expression is evaluated (executed) once unconditionally at the beginning of the loop. • In the beginning of each iteration, condition expression is evaluated. • If it evaluates to TRUE, the loop continues and the nested statements are executed. If it evaluates to FALSE, the execution of the loop ends. • At the end of each iteration, end expression is evaluated (executed).

Code before Initial expression loop false true condition Code infor-loop-block End expression Code after Flow Control (10) • for loop

Flow Control (11) • for loop <html> <head> <title>Flow Control</title> </head> <body> <?php $sum = 0; for ($i = 1; $i <= 10; $i++) { $sum += $i; } echo "Sum 1 to 10 is $sum"; ?> </body> </html>

Flow Control (12) • while while (condition) { statements } • while loops are the simplest type of loop in PHP • It tells PHP to execute the nested statement(s) repeatedly, as long as the while expression evaluates to TRUE. • The value of the expression is checked each time at the beginning of the loop.

Code before loop false true condition Code inwhile-block Code after Flow Control (13) • while

Flow Control (14) • while <html> <head> <title>Flow Control</title> </head> <body> <?php $sum = 0; $i = 1; while ($i <= 10) { $sum += $i; $i++; } echo "Sum 1 to 10 is $sum"; ?> </body> </html>

Flow Control (15) • do-while do { statements } while (condition); • do-while loops are very similar to while loops, except the truth expression is checked at the end of each iteration instead of in the beginning. • the truth expression is only checked at the end of the iteration, if it evaluates to FALSE, then the loop execution ends.

Code before loop Code indo-while-block true condition false Code after Flow Control (16) • do-while

Flow Control (17) • do-while <html> <head> <title>Flow Control</title> </head> <body> <?php $sum = 0; $i = 0; do { $i++; $sum += $i; } while ($i < 10); echo "Sum 1 to 10 is $sum"; ?> </body> </html>

Flow Control (18) • break • break ends execution of the current for, foreach, while, do-while or switch structure. • break accepts an optional numeric argument which tells it how many nested enclosing structures are to be broken out of. • continue • continue is used within looping structures to skip the rest of the current loop iteration and continue execution at the condition evaluation and then the beginning of the next iteration. • continue accepts an optional numeric argument which tells it how many levels of enclosing loops it should skip to the end of.

Flow Control (19) • break & continue <?php while (condition1) { for (initial; condition2; end) { if (condition3) continue 2; elseif (condition4) { continue; } } if (condition5) { continue; } elseif (condition6) { break; } } ?>

Chapter 2: PHP Language (I)