Open Source Server Side Scripting ECA 236 Open Source Server Side Scripting Control Structures, Operators, and Functions

Open Source Server Side Scripting 2 ECA 236 if statement if ( condition ){ statements; } if ( $dogName == “Halle” ){ echo “You are a Golden Retriever”; }

Open Source Server Side Scripting 3 ECA 236 if / else statements if( condition ){ statement1; } else{ statement2; } if( $dogName = = “Halle” ){ echo “You are a Golden Retriever”; } else{ echo “You are not my dog”; }

Open Source Server Side Scripting 4 ECA 236 if / elseif / else statements if( condition1 ){ statement1; } elseif ( condition2 ){ statement2; } else{ statement3; } if( $dogName = = “Marley” ){ echo “You are a Border Collie”; } elseif( $dogName = = “Halle” ){ echo “You are a Golden Retriever”; } elseif( $dogName = = “Boo” ){ echo “You are a Monster”; } else{ echo “You are not my dog”; }

Open Source Server Side Scripting 5 ECA 236 Nested if statements if( condition1 ){ if( conditionA ){ statementA; } if( conditionB ){ statementB; } } // end outer if else{ statement; }

Open Source Server Side Scripting 6 ECA 236 Comparison Operators SymbolMeaningExample = equal to $x = = $y ! = not equal to $x ! = $y < less than $x < $y > greater than $x > $y < = less than or equal to $x < = $y > = greater than or equal to $x > = $y

Open Source Server Side Scripting 7 ECA 236 Logical Operators SymbolMeaningExample &&and( $x = = $y ) && ( $z > 13 ) | or( $x > $y ) | | ( $z < = 47 ) !not! ( $x < $y )

Open Source Server Side Scripting 8 ECA 236 Operator Precedence OperatorAssociativity ( )N/A [ ]right ! ++ – –right * / %left + –.left < <= N/A == ! =N/A &&left | left ? :left = += – = *= /= %=.=left

Open Source Server Side Scripting 9 ECA 236 switch statements switch ( condition) { case “case 1”: statements; break; case “case 2”: statements; break; case “case 3”: statements; break; default: statements; break; } // end switch

Open Source Server Side Scripting 10 ECA 236 switch example switch ( $dogName ) { case “Marley”: echo “ You are a Border Collie. ”; break; case “Halle”: echo “ You are a Golden Retriever. ”; break; case “Boo”: echo “ You are a Monster. ”; break; default: echo “ You aren’t one of my dogs. ”; break; } // end switch

Open Source Server Side Scripting 11 ECA 236 Embedded PHP <?php if( $dogName == “Marley” ) { ?> You are a Border Collie. <?php } elseif( $dogName == “Halle” ) { ?> You are Golden Retriever. <?php } else { ?> You aren’t one of my dogs. <?php } ?> <?php switch ( $dogName ) { case “Marley”: ?> You are a Border Collie. <?php break; case “Halle”: ?> You are a Golden Retriever. <?php break; default: ?> You aren’t one of my dogs. <?php break; } ?>

Open Source Server Side Scripting 12 ECA 236 while loop while( condition ){ statements; } $counter = 1; while( $counter <= 13 ){ echo “$counter ”; $counter ++; } // end while

Open Source Server Side Scripting 13 ECA 236 for loop for( expression1; condition; expression2 ){ statements; } for( $counter = 1; $counter <= 21; $counter++ ){ echo $counter. ‘, ‘ ; if( $counter % 5 = = 0 ){ echo ‘ ’; } // end if } // end for

Open Source Server Side Scripting 14 ECA 236 do…while loop do statements; while( condition ) $counter = 1; do{ echo “$counter ”; } while( $counter > 13 )

Open Source Server Side Scripting 15 ECA 236 Control Structures  Two other loops are each( ) and foreach( ) which are used with arrays  To stop executing a loop use the break; statement  To stop the execution of an entire PHP script, use the exit; statement

Open Source Server Side Scripting 16 ECA 236 Programmer-defined Functions  Why create functions  reusable code  easier to test and debug  Functions:  define using function keyword  naming follows same rules as variables  names are case-insensitive  can be made to “reply” to the code which called it by returning a value

Open Source Server Side Scripting 17 ECA 236 Programmer-defined Functions cont…  syntax to create a function:  syntax to call a function: function function_name( ) { statements; } function_name( )

Open Source Server Side Scripting 18 ECA 236 Programmer-defined Functions cont…  arguments or parameters  functions can be written to take more than one argument  failure to send correct number of arguments results in an error  use return statement to return a value $x = 3; $y = 4; $z = multiplyThem( $x, $y ); function multiplyThem( $n1, $n2 ) { $product = $n1 * $n2; return $product; }

Open Source Server Side Scripting 19 ECA 236 Programmer-defined Functions cont…  default arguments  setting a default value for an argument makes it optional  passed values overwrite the default  place default arguments last in function definition $x = 3; $z = multiplyThem( $x ); function multiplyThem( $n1, $n2 = 10 ) { $product = $n1 * $n2; return $product; }

Open Source Server Side Scripting 20 ECA 236 Programmer-defined Functions cont…  variable scope  the scope of a variable used in a function is local to the function by default  to create a global variable use global keyword function multiplyThem( $n1, $n2 = 10 ) { global $product; $product = $n1 * $n2; return $product; }