PHP I : Control Structures

Follow this lesson in Ullman Chapter 6. The scripts are located in the 06 directory.

See the pages register.html and handle_reg.php described on Ullman pages 114ff.

 

Operators

PHP Operators: Tests of Equality and so forth
Operator	Usage	Type
+	Addition	Arithmetic
–	Subtraction	Arithmetic
*	Multiplication	Arithmetic
/	Division	Arithmetic
%	Modulus (remainder after division)	Arithmetic
++	Increment (add 1)	Arithmetic
—	Decrement (subtract 1)	Arithmetic
=	Assignment	Assignment
==	Equality (for testing)	Comparison
!=	Inequality	Comparison
<	Less than	Comparison
>	Greater than	Comparison
<=	Less than or equal to	Comparison
>=	Greater than or equal to	Comparison
!	Negation; negates any test	Logical
AND &&	And	Logical
OR ||	Or	Logical
XOR	Or NOT	Logical
.	Concatenation	String
.=	Concatenate to (put on the end of) the current value	Concatenation and Assignment
+=	Add to the current value	Concatenation and Arithmetic
-=	Subtract from the current value	Concatenation and Arithmetic

See the PHP.net manual page on Operators at http://us2.php.net/manual/en/language.operators.php

 

Using the if conditional

if (condition) {
#do stuff
}

or:

if (condition)
{
#do stuff
}

 

Things you can test

Is a variable empty?

empty()
# var is null, 0 or “”
# Returns TRUE or FALSE

Is a variable not null?

isset()
# var is not null
# var can be 0 or “”
# Returns TRUE or FALSE

Is a variable numeric?

is_numeric()
# var is numeric
# Returns TRUE or FALSE

Is a variable an array?

is_array()
# var is an array
# Returns TRUE or FALSE

Is a variable a string?

is_string()
# var is a string
# Returns TRUE or FALSE

Is a variable an integer?

is_integer()
# var is an array
# Returns TRUE or FALSE

Is a variable a real date?

checkdate()
# var is a truly possible date
# Returns TRUE or FALSE

 

Using if/else

if (condition) {
#do stuff
} else {
#do different stuff
}

 

Using if/elif/else

if (condition) {
  # do option a
} elif (condition) {
  # do option b
} else {
  # do some default option
}

 

Using the Switch Conditional

switch ($variable) {
  case “value1” :
    option1_code();
    break;
  case “value2” :
    option2_code();
    break;
  default :
    default_code();
    break;
}

 

The for Loop

for (starting_value, ending_value, increment) {
   # do some stuff each time
}

It may make more sense like this:

for ($x = 1, $x < 10, $x++) {
   # do some stuff each time
   print “\$x is now $x”;
}

 

The foreach Loop

foreach ($array as $key => $value) {
   print “Key is $key. \n Value is $value.”;
}

 

The while Loop

while (this_condition_is_true) {
   #do stuff
}

A while loop can’t set initial conditions and can’t execute closing expressions.

A while loop may not execute even once if the initial condition is false!

 

The do…while Loop

do {
   # stuff
} while (condition_is_true)

 

A do…while loop will always execute at least once.

 

Break!  Continue!  Exit!  and  Die!

Break: Exit the loop. Code that follows the loop executes.

Continue: Leave the current point in the loop. Loop continues to execute.

Exit: Stop executing all PHP code! – and don’t send following HTML code.

Die: Stop executing all PHP code! – and don’t send following HTML code.

 

Outside of class:

Review Chapter 6 of Ullman.