Scripting Languages and PHP

1
Scripting Languages and PHP
2
Origins

• Rasmus Lerdorf
• Personal Home Pages.
• Zeev Surashi and Andi Gutmans
• Open Source
• PHP version 4
• Full information on which facilities installed
  phpinfo()

3
PHP as a programming language

• Evolved not designed
• Cross-platform
• Scripting language
• designed to support a specific task
• untyped variables (but values are typed)
• implicit variable declaration
• implicit type conversion
• stored only as script files

4

• Procedural (not event driven)
• -runs from start to finish
• Procedural (not object-oriented)
• Library of function not classes
• C-style language

5

• Free format - white space is ignored
• Statements are separated by semi-colon
• Statements grouped by
• Comments begin with // or a set of comments /
  /
• Assignment is a6
• Relational operators are ,lt , gt ( not a
  single equal)
• Control structures include if (cond) .. else
  , while (cond) .. , for(sstartcond,
  increment, endcond)
• Arrays are accessed with x4 is the
  5th element of the array x indexes start at 0
• Associative Arrays (or hash arrays in Perl,
  sparse arrays in data structures) are accessed in
  the same way yfred
• Functions are called with the name followed by
  arguements in a fixed order enclosed in ( )
  substr(fred,0,2)
• Case sensitive - fred is a different variable
  to FRED

6

• HTML-embedded
• PHP scripts are essentially HTML pages with the
  occasional section of PHP script.
• PHP script is enclosed in the tag pair
• lt?php and ?gt
• Scripts may be short
• lth1gtDepartures from lt?php echo date( Hi ) ?gt
  lt/h1gt
• or long
• (the rest of the program)

7
Server-side
PHP processor
Web server
Browser
get Myprog.php?a8bfred
Locate file Determine its PHP Set up context URL
variables etc
Interpret script Access context
Script output
HTML
8
PHP-Server interaction

• Accessing the input data
• Parameters in the URL become variables of the
  same name. a6 bfred
• Parameters in a array _GETa
• Accessing Environment Variables
• PHP_SELF is the program name
• HTTP_USER_AGENT is the browser
• phpinfo() to list all of them installed
  libraries
• Producing Output
• lth1gtAnnouncementslt/h1gt
• lt?php print(lth1gtAnnouncementslt/h1gt) ?gt
• lt?php print lth1gtAnnouncementslt/h1gt ?gt
• lt?php echo lth1gtAnnouncementslt/h1gt ?gt

9
User defined functions

• function double(n)
• return n2
• which we can use as
• x double(y)
• or
• xdouble(4)
• place common functions in a separate file and
  include it
• include(myfuns.php)

10
PHP tasks

• Data
• Script variables - a
• Session variables later
• Persistant use a database

11
String Handling

• String literals (constants) enclosed in double
  quotes or single quotes
• Within , variables are replaced by their value
  called variable interpolation. My name is
  name, I think
• Within single quoted strings, interpolation
  doesnt occur
• Strings are concatenated (joined end to end) with
  the . operator key.board is keyboard
• Standard functions exist strlen(), substr() etc
• Regular expressions be used for complex pattern
  matching
• Values of other types can be easily converted to
  and from strings numbers implicitly converted
  to strings in a string context.

12
Function library

• Basic tasks
• String Handling
• Mathematics random numbers, trig functions..
• Regular Expressions
• Date and time handling
• File Input and Output
• And more specific functions for-
• Database interaction
• MySQL, Oracle, Postgres, Sybase, MSSQL ..
• Encryption
• Text translation
• Spell-checking
• Image creation
• XML

13
lthtmlgtltheadgtlttitlegtBus departures from
Frenchaylt/titlegtltmeta http-equivrefresh
content60gtlt/headgtltbodygtlth1gtFrenchay
Buseslt/h1gtlth2gtlt?php echo date ("Hi") ?gtlt/h2gt
14
lt?php// form variables none// connect to the
database   server  "shares.cems.uwe.ac.uk"   
user"cwstudent"   password"cwstudent"   d
b"Bus"   if(!(dblinkmysql_connect(server,u
ser,password)))      print("mysql_connect
failedltbrgt\n")      query "select from
departure where dtime gt current_time() order by
dtime limit 10"   if(!(dbresult  mysql_db_que
ry(db,query,dblink)))         print("ltbgtquery
failedlt/h4gtltbrgt\n")        print(mysql_error() 
. "ltbrgt\n")   
15
   print("lttable border1gt")   print("lttrgtltthgtRo
utelt/thgtltthgtTimelt/thgtlt/trgt")   while(departure
mysql_fetch_object(dbresult))        print("ltt
rgt")       print("lttdgtdeparture-gtroutenolt/tdgt")
       print("lttdgtdeparture-gtdtimelt/tdgt")    
   print("lt/trgt\n")          print("lt/tablegt"
)  // close the database   mysql_close(dblin
k)?gtlt/bodygtlt/htmlgt