PHP Control Structures Part 2

1
PHP Control Structures Part 2
2
Conditional Complexity

• You can imagine that conditionals can get quite
  complex very quickly.
• Imagine a scenario where you need to perform a
  specific action based upon the contents of a
  menu with 12 .

3
A Complex if-elsif-else Conditional
// Get the horoscope sign. if (month 1) //
January if (day 'Caprico1rn' else sign 'Aquarius'
elseif (month 2) // February if (day
'Pisces' elseif (month 3) if
(day sign 'Aries' elseif (month 4)
if (day sign 'Taurus' elseif (month 5)
if (day sign 'Gemini' elseif (month 6)
if (day sign 'Cancer' elseif (month 7)
if (day sign 'Leo' elseif (month 8)
if (day sign 'Virgo' elseif (month 9)
if (day sign 'Libra' elseif (month 10)
if (day sign 'Scorpio' elseif (month
11) if (day else sign 'Sagittarius' elseif
(month 12) if (day 'Sagittarius' else sign
'Capricorn'
4
Switch conditional

• The switch() conditional can make code cleaner
  and easier to read.

switch (name) case "afonzarelli" role
'admin' break case "rmouth" role
'flunky' break case "pwebber" role
'flunky' break default role ''
echo 'Name undefined.' break
if (name) 'afonzarelli') role
'admin' elseif (name 'rmouth') role
'flunky' elseif(name 'pwebber') role
'flunky' else role '' echo 'Name
undefined.'
These two constructs do exactly the same thing.
5
Switch conditional

• switch() uses the value of z as its condition,
  first checking if z "value1", and if so,
  executing statement(s) and then breaking out of
  the switch() conditional.

switch (z) case "value1" statement1(s)
break
case "value2" statements(s) break
default statement(s) break

6
Looping Control Structures

• Loops provide a mechanism for executing a section
  of code repeatedly.
• PHP supports three kinds of loops for, while,
  and foreach.

7
for Loop

• for loops perform specific statements for a
  determined number of iterations.
• for (initial expression, condition closing
  expression)
• statement(s)
• Example
• for (v 1 v
• print "v"

8
while Loop

• while loops executes the loop until the condition
  is false.
• Used frequently for retrieving values from a
  database or file.
• i 1
• while (i
• echo i / printed value is
• i before the increment
• (post-increment) /

9
do-while Loop

• Guarantees that the statements are executed at
  least once
• z1
• do
• print "z"
• z
• while (z 0)

Executes this statement, even though z1
10
foreach Loop

• Used extensively to grab and manipulate values
  from arrays.
• There are two syntaxes the second is a minor but
  useful extension of the first .
• foreach (array_expression as value) 
   statementforeach (array_expression as key
  value)   statement
• The first form loops over the array given by
  array_expression. On each loop, the value of the
  current element is assigned to value and the
  internal array pointer is advanced by one
• The second form does the same thing, except that
  the current element's key will be assigned to the
  variable key on each loop.

11
Break, Die, Exit, Continue

• break exits the current structure, be it a
  switch, an if-else conditional, or a loop.
• continue terminates the current iteration of the
  loop. Any remaining statements within the loop
  aren't executed, and the loop's condition is
  checked again to see if the loop should be
  entered.

12
Exit and Die

• exit terminates the execution of the script. All
  code after exit or die remains unexecuted
  (including HTML). die is an alias for exit
• filename '/path/to/data-file.txt'
• file fopen(filename, 'r') or exit("color'red'unable to open file
  (filename)")

13
Example of Continue

• for (counter 0 counter
• test counter
• print "counter counter
  "
• if( test 6 )
• echo "skipped...
  
  "
• continue / Jumps to top w/o executing
  the
• rest of the statements in
  this
• conditional /
• / This line will only print if
• test does not contain 6 /
• print "test test
  
  "
• print "DONE!"