PHP String Functions, User Functions and Pulling it All Together

1. PHP String Functions, User Functionsand Pulling it All Together Chapters 4 & 5

2. <?php // check for submit if (!isset($_POST['submit'])) {     // and display form ?> <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="POST">     <input type="checkbox" name="artist[]" value="Bon Jovi">Bon Jovi     <input type="checkbox" name="artist[]" value="N'Sync">N'Sync     <input type="checkbox" name="artist[]" value="Boyzone">Boyzone     <input type="checkbox" name="artist[]" value="Britney Spears">Britney Spears     <input type="checkbox" name="artist[]" value="Jethro Tull">Jethro Tull     <input type="checkbox" name="artist[]" value="Crosby, Stills & Nash">Crosby, Stills & Nash     <input type="submit" name="submit" value="Select">     </form> <?php     } else {     // or display the selected artists     // use a foreach loop to read and display array elements     if (is_array($_POST['artist'])) {         echo 'You selected: <br />';  foreach ($_POST['artist'] as $a) {            echo "<i>$a</i><br />";             }         }     else {         echo 'Nothing selected';     } } ?> Using an array to process multiple checkbox entries.

3. Functions • Very straightforward in PHP • Functions are code modules within your PHP scripts that are useful for: • Repetitive tasks • Clarifying (by segmenting) your code • Points to cover: • Placement • Parameters • Return values • Scope

4. Example 1 <?php // define a function functionmyStandardResponse() {     echo "Get lost, jerk!<br /><br />"; } // on the bus echo "Hey lady, can you spare a dime? <br />"; myStandardResponse(); // at the office echo "Can you handle Joe's workload, in addition to your own, while he's in Tahiti for a month? You'll probably need to come in early and work till midnight...<br />"; myStandardResponse(); // at the party echo "Hi, haven't I seen you somewhere before?<br />"; myStandardResponse(); ?>

5. About Example 1 • Placed above any calls to it • Has no parameters • Does not return any value • Functions that return no value are most often used to display a message • That’s what this example does

6. Function Format functionfunction_name (optional function arguments/parameters) {     statement 1...;     statement 2...;     .     statement n...; }

7. Example 2 – one argument/parameter <?php // define a function function getCircumference($radius) {     echo "Circumference of a circle with radius $radius is ".sprintf("%4.2f", (2 * $radius * pi()))."<br />"; } // call the function with an argument getCircumference(10); // call the same function with another argument getCircumference(20); ?>

8. Example 3 – two parameters <?php // define a function function changeCase($str, $flag) {     /* check the flag variable and branch the code */     switch($flag) {         case 'U':             print strtoupper($str)."<br />";             break;         case 'L':             print strtolower($str)."<br />";             break;         default:             print $str."<br />";             break;     } } // call the function changeCase("The cow jumped over the moon", "U"); changeCase("Hello Sam", "L"); ?> Parameter order matters!

9. Example 4 – return value <?php // define a function function getCircumference($radius) {     // return value  return (2 * $radius * pi()); } /* call a function with an argument and store the result in a variable */ $result =getCircumference(10); /* call the same function with another argument and print the return value */ printgetCircumference(20); ?> Only one value can be returned this way!

10. Example 5 – returning an array <?php /* define a function to accept a list of email addresses */ function getUniqueDomains($list) {     /* iterate over the list, split addresses, add domain part to another array */     $domains = array(); //declare array $domains     foreach ($list as $l) {         $arr = explode("@", $l);         $domains[ ] = trim($arr[1]);     }     // remove duplicates and return  return array_unique($domains); } // read email addresses from a file into an array $fileContents = file("data.txt"); /* pass the file contents to the function and retrieve the result array */ $returnArray = getUniqueDomains($fileContents); // process the return array foreach ($returnArray as $d) {     print "$d, "; } ?>

11. Example 6 – multiple parameters <?php // define a function function introduce($name, $place) {     print "Hello, I am $name from $place"; } // call function introduce("Moonface", "The Faraway Tree"); ?>

12. Example 7 – default values <?php // define a function function introduce($name="John Doe", $place="London") {     print "Hello, I am $name from $place"; } // call function introduce("Moonface"); ?>

13. Example 7 – variable # arguments • <?php • // define a function • function someFunc() { •     // get the arguments •     $args = func_get_args(); •     // print the arguments •     print "You sent me the following arguments:"; • foreach ($args as $arg) { •         print " $arg "; •     } •     print "<br />"; • } • // call a function with different # arguments • someFunc("red", "green", "blue"); • someFunc(1, "soap"); • ?>

14. Example 8 - Scope <?php // define a variable in the main program $today = "Tuesday"; // define a function function getDay() {     // define a variable inside the function  $today = "Saturday";     // print the variable     print "It is $today inside the function<br />"; } // call the function getDay(); // print the variable print "It is $today outside the function"; ?>

15. Example 9 – global scope <?php // define a variable in the main program $today = "Tuesday"; // define a function function getDay() {     // make the variable global global $today;     // define a variable inside the function $today = "Saturday";     // print the variable     print "It is $today inside the function<br />"; } // print the variable print "It is $today before running the function<br />"; // call the function getDay(); // print the variable print "It is $today after running the function"; ?> Once a variable is declared global, it is available at the global level, and can be manipulated both inside and outside a function.

16. Example 10 – arrays as arguments • <?php • // define a function • function someFunc() { •     // get the number of arguments passed •     $numArgs = func_num_args(); • // get the arguments •     $args = func_get_args(); •     // print the arguments •     print "You sent me the following arguments: "; •  for ($x = 0; $x < $numArgs; $x++) { •         print "<br />Argument $x: "; •         /* check if an array was passed and, if so, iterate and print contents */ •         if (is_array($args[$x])) { •             print " ARRAY "; •             foreach ($args[$x] as $index => $element) { •                 print " $index => $element "; •             } •         } •         else { •             print " $args[$x] "; •         } •     } • } • // call a function with different arguments • someFunc("red", "green", "blue", array(4,5), "yellow"); • ?>

17. Example 11 – parameter passing <?php // create a variable $today = "Saturday"; // function to print the value of the variable function setDay($day) {     $day = "Tuesday";     print "It is $day inside the function<br />"; } // call function setDay($today); // print the value of the variable print "It is $today outside the function"; ?> Passing $today by value

18. Example 12 – parameter passing <?php // create a variable $today = "Saturday"; // function to print the value of the variable function setDay(&$day) {     $day = "Tuesday";     print "It is $day inside the function<br />"; } // call function setDay($today); // print the value of the variable print "It is $today outside the function"; ?> Passing $today by reference

19. String Processing • One of the most common uses of PHP is the processing of form data submitted by users. • Validation is extremely important • So is precision

20. Miscellany • Concatenation – uses . or enclose all fields within double quotes. • Including escape sequences in strings • Use double quotes for “\\” - inserts backslash “\$” - inserts dollar sign “\r” – inserts carriage return “\”” – inserts double quote “\t” – inserts tab “\n” – inserts new line

21. Popular String Functions 1 String length: • strlen(string_to_check) String searches: • strpos(string_to_search, string_to_search_for) • Returns first position of found string; if not found, returns FALSE • Use strict inequality check: !== (in place of !=) • Variation: stripos – it’s case insensitive • strstr(string_to_search, string_to_search_for) • Returns a substring from the beginning of the found string until the end of searched string • Variation: stristr • Also, strchr – search for substring starting with one specific character

22. Popular String Functions 2 Extraction of substring (no search): • substr(str_to_search, start_pos, length) Replacing characters & substrings: • str_replace(str_to_replace, repl_str, string) • str_ireplace • substr_replace(string, repl_str, start_pos, length)

23. Popular String Functions 3 Pulling strings apart: • strtok(string, separator) • Follow with strtok(separator) • Ex: $s = “ABC*DEF*GHI*JKL*MNO”; $s_token = strtok($s,”*”); while ($s_token != NULL) { echo “$s_token<br / >”; $s_token = strtok(“*”); }

24. Popular String Functions 4 Converting between arrays and strings: • explode(separator, string) • Start with string, create array • implode(separator, array) • Start with array, create string

25. Popular String Functions 5 Exact comparisons: • strcmp(str1, str2) - case sensitive • strcasecmp(str1, str2) - case insensitive Check for similar text: • similar_text(str1, str2) • Returns # characters in common • soundex and metaphone

26. Popular String Functions 6 • nl2br(string) • Replaces all newlines with breaks