PHP String Functions, User Functions

and Pulling it All Together

Chapters 4 & 5

<?php// check for submitif (!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.

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

Example 1<?php// define a functionfunction myStandardResponse() {    echo "Get lost, jerk!<br /><br />";}

// on the busecho "Hey lady, can you spare a dime? <br />";myStandardResponse();

// at the officeecho "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 partyecho "Hi, haven't I seen you somewhere before?<br />";myStandardResponse();?>

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

Function Format

function function_name (optional function arguments/parameters) {

    statement 1...;

    statement 2...;

    .

    statement n...;

}

Example 2 – one argument/parameter

<?php// define a functionfunction getCircumference($radius) {    echo "Circumference of a circle with radius $radius

is ".sprintf("%4.2f", (2 * $radius * pi()))."<br />";}// call the function with an argumentgetCircumference(10);// call the same function with another argumentgetCircumference(20);?>

Example 3 – two parameters<?php// define a functionfunction 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!

Example 4 – return value

<?php// define a functionfunction 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 */print getCircumference(20);?>

Only one value can be returned this way!

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 arrayforeach ($returnArray as $d) {    print "$d, ";}?>

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");

?>

Example 7 – default values

<?php// define a functionfunction introduce($name="John Doe",

$place="London") {    print "Hello, I am $name from $place";}// call functionintroduce("Moonface");?>

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");• ?>

Example 8 - Scope

<?php// define a variable in the main program$today = "Tuesday";// define a functionfunction getDay() {    // define a variable inside the function    $today = "Saturday";    // print the variable    print "It is $today inside the function<br />";}// call the functiongetDay();// print the variableprint "It is $today outside the function";?>

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 variableprint "It is $today before running the function<br />";// call the functiongetDay();// print the variableprint "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.

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");• ?>

Example 11 – parameter passing

<?php// create a variable$today = "Saturday";// function to print the value of the variablefunction setDay($day) {    $day = "Tuesday";    print "It is $day inside the function<br />";}// call functionsetDay($today);// print the value of the variableprint "It is $today outside the function";?>

Passing $today by value

Example 12 – parameter passing

<?php// create a variable$today = "Saturday";// function to print the value of the variablefunction setDay(&$day) {    $day = "Tuesday";    print "It is $day inside the function<br />";}// call functionsetDay($today);// print the value of the variableprint "It is $today outside the function";?>

Passing $today by reference

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

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

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

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)

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(“*”);

}

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

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

Popular String Functions 6

• nl2br(string)– Replaces all newlines with breaks