Adding line breaks

If you use PHP to generate quite a lot of HTML and text for your page, you need to be a bit careful how you structure the output. To see what I mean, first check out the following PHP code:

<?php

$str1 = "<div>What does PHP stand for?</div>";

$str2 = "<div>It's a <i>recursive acronym</i>:</div>";

$str3 = "<div>PHP: Hypertext Preprocessor</div>";

echo $str1, $str2, $str3;

?>

This code declares three strings — all div elements with text — and uses echo to output them. Figure 1-4 shows two browser windows. In the upper window, you can see that the output from the preceding code looks fine. However, the lower window shows the source code for the page and, as you can see, all the output text and tags appear on a single line.

To make the source code text easier to read, you should add line breaks to your PHP output strings. You insert a line break using the newline character (which doesn't appear on the web page). Here’s the revised code (with added to the end of the $str1 and $str2 variables), and Figure 1-5 shows that the source code now appears on multiple lines:

<?php

$str1 = "<div>What does PHP stand for?</div> ";

$str2 = "<div>It's a <i>recursive acronym</i>:</div> ";

$str3 = "<div>PHP: Hypertext Preprocessor</div>";

echo $str1, $str2, $str3;

?>

The newline code only works in a string that uses double quotation marks. If you use single quotation marks, PHP outputs the characters instead of creating a newline. For example:

echo 'Ready Set Go!';

The output of this statement is

Ready Set Go!

Mixing and escaping quotation marks

You can enclose PHP string literals in either double quotation marks or single quotation marks, but not both:

$order = "Double espresso"; // This is legal

$book = 'A Singular Man'; // So's this

$weather = 'Mixed precipitation"; // This is not legal

However, mixing quotation mark types is sometimes necessary. Consider this:

$tag = "<a href="https://wordspy.com">";

That statement will cough up an error because PHP thinks the string ends after the second double quotation mark, so it doesn't know what to do with the rest of the statement. To solve this problem, swap the outer double quotation marks for singles:

$tag = '<a href="https://wordspy.com/">';

That works fine. However, what if you want to add some line breaks, as I describe in the previous section:

$tag = '<a href="https://wordspy.com/"> Word Spy </a>';

Nice try, but newlines ( ) only work when they’re enclosed by double quotation marks. The statement above will not include any line breaks and will show the link text as Word Spy . Sigh.

All is not lost, however, because you can convince the PHP processor to treat a quotation mark as a string literal (instead of a string delimiter), by preceding the quotation mark with a backslash (). This is known in the trade as escaping the quotation mark. For example, you can fix the previous example by enclosing the entire string in double quotation marks (to get the newlines to work) and escaping the double quotation marks used for the <a> tag's href value:

$tag = "<a href="https://wordspy.com/"> Word Spy </a>";

Outputting variables in strings

One very useful feature of PHP strings is that you can insert a variable name into a string and the PHP processor will handily replace the variable name with its current value. Here’s an example:

<?php

$title = "Inflatable Dartboard Landing Page";

$tag = "<title>$title</title>";

echo $tag;

?>

The output of this code is

<title>Inflatable Dartboard Landing Page</title>

Some folks call this interpolating the variable, but we’ll have none of that here.

Alas, variable value substitution only works with strings enclosed by double quotation marks. If you use single quotation marks, PHP outputs the variable name instead of its value. For example, this

<?php

$title = "Inflatable Dartboard Landing Page";

$tag = '<title>$title</title>';

echo $tag;

?>

outputs this:

<title>$title</title>

Outputting long strings

If you have a long string to output, one way to do it would be to break up the string into multiple variables, add newlines at the end of each, if needed, and output each variable.

That works, but PHP offers a shortcut method where you output everything as a single string, but span the string across multiple lines. For example, I can take the final code from the “Adding line breaks” section and achieve the same result by rewriting it as follows:

<?php

$str1 = "<div>What does PHP stand for?</div>

<div>It's a <i>recursive acronym</i>:</div>

<div>PHP: Hypertext Preprocessor</div>";

echo $str1;

?>

The implied newlines at the end of the second and third lines are written to the page, so the page source code will look exactly the same as it does in Figure 1-5.

Outputting really long strings

For a super-long string, you can use PHP’s here document (or heredoc) syntax:

<<<terminator

Super-long string goes here

terminator;

• terminator: This is a label that marks the beginning and end of the string. The label at the end must appear on a line by itself (except for the closing semicolon), with no whitespace before or after the label.

This syntax also supports variable names, so if you include a variable in the string, PHP will substitute the current value of that variable when it outputs the string.

Here's an example:

<?php

$author = "Rasmus Lerdorf";

$str = <<<END_OF_STRING

<blockquote>

In the end, what I think set PHP apart in the early

days, and still does today, is that it always tries

to find the shortest path to solving the Web

problem. It does not try to be a general-purpose

scripting language and anybody who's looking to

solve a Web problem will usually find a very direct

solution through PHP. Many of the alternatives that

claim to solve the Web problem are just too complex.

When you need something up and working by Friday so

you don't have to spend all weekend leafing through

800-page manuals, PHP starts to look pretty good.

—$author

</blockquote>

END_OF_STRING;

echo $str;

?>

Notice that I declared a variable named $author, and then I included that variable name in the string (it’s on the second-last line of the string). PHP treats a heredoc string as though it was enclosed by double quotation marks, so it substitutes the variable value in the output. Figure 1-6 shows the result.

Declaring arrays

PHP gives you a bunch of ways to declare and populate arrays. Probably the most straightforward method is to assign values to explicit index numbers:

$array_name[index] = value;

• $array_name: The name of the array variable
• index: The optional array index number you want to work with
• value: The value you want to assign to the array index number

For example, the following statements assign string values to the first three elements (that is, the elements at array indexes 0, 1, and 2) of an array named $team_nicknames:

$team_nicknames[0] = 'Banana Slugs';

$team_nicknames[1] = 'Fighting Okra';

$team_nicknames[2] = 'Golden Flashes';

Notice in the syntax that I said the index parameter was optional. If you leave it out, PHP assigns the index numbers automatically. So, as long as the variable $team_nicknames doesn't already contain any elements, the following code is equivalent to the preceding code:

$team_nicknames[] = 'Banana Slugs';

$team_nicknames[] = 'Fighting Okra';

$team_nicknames[] = 'Golden Flashes';

To add multiple array values in a single statement, you can use PHP’s array keyword:

$array_name = array(value1, value1, etc.);

• $array_name: The name of the array variable
• value1, value2, etc.: The values you want to assign to the array

Here's an example:

<?php

$team_nicknames = array('Banana Slugs', 'Fighting Okra', 'Golden Flashes');

echo $team_nicknames[0];

?>

The output of this code is

Banana Slugs

Giving associative arrays a look

Most PHP arrays use numeric index values, but in web development work it’s often handy to work with string index values, which are called keys. An array that uses keys instead of a numeric index is called an associative array, because you’re associating each key with a value to create an array of key/value pairs.

Here’s an example:

<?php

$team_nicknames['Santa Cruz'] = 'Banana Slugs';

$team_nicknames['Delta State'] = 'Fighting Okra';

$team_nicknames['Kent State'] = 'Golden Flashes';

echo $team_nicknames['Delta State'];

?>

The output of this code is

Fighting Okra

To create an associative array using the array keyword, you assign each key/value pair using the => operator, as in this example:

<?php

$team_nicknames = array('Santa Cruz' => 'Banana Slugs', 'Delta State' => 'Fighting Okra', 'Kent State' => 'Golden Flashes');

echo $team_nicknames['Kent State'];

?>

The output of this code is

Golden Flashes

Outputting array values

You can use the echo or print keyword to output individual array values. However, what if you want to see all the values stored in an array? Rather than, say, looping through the array, PHP offers the print_r() function, which outputs the current value of a variable:

print_r($variable);

• $variable: The name of the variable you want to output

If you use an array as the print_r() parameter, PHP outputs the contents of the array as key/value pairs. For example, the following code

<pre>

<?php

$team_nicknames = array('Banana Slugs', 'Fighting Okra', 'Golden Flashes');

print_r($team_nicknames);

?>

</pre>

outputs the following:

Array

(

[0] => Banana Slugs

[1] => Fighting Okra

[2] => Golden Flashes

)

Note that I surrounded the PHP code with the <pre> tag to get the output on multiple lines rather than a single hard-to-read line.

Sorting arrays

If you need your array values sorted alphanumerically, PHP offers a handful of functions that will get the job done. The function you use depends on the type of sort you want (ascending or descending) and whether your array uses numeric indexes or string keys (that is, an associative array).

For numeric indexes, you can use the sort() function to sort the values in ascending order (0 to 9, then A to Z, then a to z), or the rsort() function to sort the values in descending order (z to a, then Z to A, then 9 to 0):

sort($array);

rsort($array);

• $array: The name of the array you want to sort

Here's an example:

<pre>

<?php

$oxymorons = array('Pretty ugly', 'Jumbo shrimp', 'Act naturally', 'Original copy');

sort($oxymorons);

print_r($oxymorons);

?>

</pre>

Here’s the output:

Array

(

[0] => Act naturally

[1] => Jumbo shrimp

[2] => Original copy

[3] => Pretty ugly

)

For associative arrays, you can use the asort() function to sort the values in ascending order (0 to 9, then A to Z, then a to z), or the arsort() function to sort the values in descending order (z to a, then Z to A, then 9 to 0):

asort($array);

arsort($array);

• $array: The name of the associative array you want to sort

Here's an example:

<pre>

<?php

$team_nicknames = array('Santa Cruz' => 'Banana Slugs', 'Delta State' => 'Fighting Okra', 'Kent State' => 'Golden Flashes');

arsort($team_nicknames);

print_r($team_nicknames);

?>

</pre>

Here’s the output:

Array

(

[Kent State] => Golden Flashes

[Delta State] => Fighting Okra

[Santa Cruz] => Banana Slugs

)

Looping through array values

PHP offers a special loop called foreach() that you can use to loop through an array’s values. Here’s the syntax:

foreach($array as $key => $value) {

Loop statements go here

}

• $array: The name of the array you want to loop through
• $key: An optional variable name that PHP uses to store the key of the current array item
• $value: A variable name that PHP uses to store the value of the current array item

Here's an example:

<?php

$team_nicknames = array('Santa Cruz' => 'Banana Slugs', 'Delta State' => 'Fighting Okra', 'Kent State' => 'Golden Flashes');

foreach($team_nicknames as $school => $nickname) {

echo "The team nickname for $school is $nickname.<br>";

}

?>

Here’s the output:

The team nickname for Santa Cruz is Banana Slugs.

The team nickname for Delta State is Fighting Okra.

The team nickname for Kent State is Golden Flashes.

Creating multidimensional arrays

A multidimensional array is one where two or more values are stored within each array element. In a one-dimensional array, the value is usually a string, number, or Boolean. Now imagine, instead, that value is an array literal. For a two-dimensional array, the general syntax for assigning an array to an array element looks like this:

arrayName[index] = Array(value1, value2);

As an example, say you want to store an array of background and foreground colors. Here's how you might declare and populate such an array:

<?php

$colorArray[0] = Array('white', 'black');

$colorArray[1] = Array('aliceblue', 'midnightblue');

$colorArray[2] = Array('honeydew', 'darkgreen');

echo $colorArray[1][1];

?>

Here’s the output:

midnightblue

Alternatively, you can declare and populate an associative array:

<?php

$colorArray['scheme1'] = Array('foreground' => 'white', 'background' => 'black');

$colorArray['scheme2'] = Array('foreground' => 'aliceblue', 'background' => 'midnightblue');

$colorArray['scheme3'] = Array('foreground' => 'honeydew', 'background' => 'darkgreen');

echo $colorArray['scheme2']['foreground'];

?>

Here’s the output:

aliceblue

Making decisions with if()

You make simple true/false decisions in PHP using the if() statement:

if (expression) {

statements-if-true

}

• expression: A comparison or logical expression that returns true or false.
• statements-if-true: The statement or statements to run if expression returns true. If expression returns false, PHP skips over the statements.

Here's an example:

if ($original_amount !== 0) {

$percent_increase = 100 * (($new_amount - $original_amount) / $original_amount);

}

To run one group of statements if the condition returns true and a different group if the result is false, use an if()…else statement:

if (expression) {

statements-if-true

} else {

statements-if-false

}

• expression: A comparison or logical expression that returns true or false
• statements-if-true: The block of statements you want PHP to run if expression returns true
• statements-if-false: The block of statements you want executed if expression returns false

Here's an example:

<?php

if ($currentHour < 12) {

$greeting = "Good morning!";

} else {

$greeting = "Good day!";

}

echo $greeting;

?>

There is a third syntax for the if()…else statement that lets you string together as many logical tests as you need:

if (expression1) {

statements-if-expression1-true

} elseif (expression2) {

statements-if-expression2-true

}

etc.

else {

statements-if-false

}

This syntax represents a rare instance where PHP and JavaScript control structures are different (however slightly): You use the keywords else if in JavaScript, but the single keyword elseif in PHP.

The following code shows a script that uses a nested if() statement.

<?php

if ($currentHour < 12) {

$greeting = "Good morning!";

} elseif ($currentHour < 18) {

$greeting = "Good afternoon!";

} else {

$greeting = "Good evening!";

}

echo $greeting;

?>

Making decisions with switch()

For situations where you need to make a whole bunch of tests (say, four or more), PHP offers the switch() statement. Here's the syntax:

switch(expression) {

case case1:

case1 statements

break;

case case2:

case2 statements

break;

etc.

default:

default statements

}

The expression is evaluated at the beginning of the structure. It must return a value (numeric, string, or Boolean). case1, case2, and so on are possible values for expression. PHP examines each case value to see whether one matches the result of expression and, if it does, executes the block associated with that case; the break statement tells PHP to stop processing the rest of the switch() statement.

Here's an example:

switch($season) {

case 'winter':

$footwear = 'snowshoes';

break;

case 'spring':

$footwear = 'galoshes';

break;

case 'summer':

$footwear = 'flip-flops';

break;

case 'fall':

$footwear = 'hiking boots';

break;

}

Looping with while()

PHP’s while() loop uses the following syntax:

while (expression) {

statements

}

Here, expression is a comparison or logical expression that determines how many times the loop gets executed, and statements represents a block of statements to execute each time through the loop.

Here's an example:

<?php

$counter = 1;

while ($counter <= 12) {

// Generate a random number between 1 and 100

$randoms[$counter - 1] = rand(1, 100);

$counter++;

}

print_r($randoms);

?>

Looping with for()

The structure of a PHP for() loop looks like this:

for ($counter = start; expression; $counter++) {

statements

}

• $counter: A numeric variable used as a loop counter
• start: The initial value of $counter
• expression: A comparison or logical expression that determines the number of times through the loop
• $counter++: The increment operator applied to the $counter variable
• statements: The statements to execute each time through the loop

Here's an example:

<?php

for ($counter = 0; $counter < 12; $counter++) {

// Generate a random number between 1 and 100

$randoms[$counter] = rand(1, 100);

}

print_r($randoms);

?>

Looping with do…while()

PHP’s do…while() loop uses the following syntax:

do {

statements

}

while (expression);

Here, statements represents a block of statements to execute each time through the loop, and expression is a comparison or logical expression that determines how many times PHP runs through the loop.

Here's an example:

<?php

$counter = 0;

do {

// Generate a random number between 1 and 100

$randoms[$counter] = rand(1, 100);

$counter++;

}

while ($counter < 12);

print_r($randoms);

?>

Passing values to functions

An argument is a value that is “sent” — or passed, in programming terms — to the function. The argument acts just like a variable, and it automatically stores whatever value is sent. Here’s an example:

display_header('notw.png');

function display_header($img_file) {

echo "<header> ";

echo "<img src="/images/$img_file" alt="News of the Word logo"> ";

echo "<h1>News of the Word</h1> ";

echo "<h3>Language news you won't find anywhere else (for good reason!)</h3> ";

echo "</header>";

}

Returning a value from a function

If your function calculates a result, you can send that result back to the statement that called the function by using a return statement:

return result;

As an example, I'll construct a function that calculates and then returns the tip on a restaurant bill:

$preTipTotal = 100.00;

$tipPercentage = 0.15;

function calculate_tip($preTip, $tipPercent) {

$tipResult = $preTip * $tipPercent;

return $tipResult;

}

$tipCost = calculate_tip($preTipTotal, $tipPercentage);

$totalBill = $preTipTotal + $tipCost;

echo "Your total bill is $$totalBill";

Rolling your own objects

Let’s take a quick look at creating custom objects in PHP. In the object-oriented world, a class acts as a sort of object “template.” A cookie cutter provides a good analogy. The cookie cutter isn’t a cookie, but, when you use it, the cookie cutter creates an actual cookie that has a predefined shape. A class is the same way. It’s not an object, but using it (or instancing it, to use the vernacular) creates an object that uses the class characteristics. These characteristics are governed by the members of the class, which are its properties and methods.

Creating an object

Given a class — whether it’s a built-in PHP class or a class that you’ve created yourself — you can create an object from the class, which is known as an instance of the class. Here’s the general format to use:

$object = new Class(value1, value2, …);

• $object: The variable name of the object
• Class: The name of the class on which to base the object
• value1, value2, etc.: The optional initial values you want to assign to the object's properties

Here’s a statement that creates an instance of the Invoice class from the previous section:

$inv = new Invoice('BONAP', 59.85, .07);

Working with object properties

You refer to an object property by using the object operator (->):

object->property

• object: The object that has the property
• property: The name of the property you want to work with

Here's an example that creates an object instance and then references the object’s customer_id property:

$inv = new Invoice('BONAP', 59.85, .07);

$current_customer = $inv->customer_id;

To change the value of a property, use the following generic syntax:

object->property = value;

• object: The object that has the property
• property: The name of the property you want to change
• value: A literal value (such as a string or number) or an expression that returns the value to which you want to set the property

Here's an example:

$inv->subtotal = 99.95;

Working with object methods

To run a method, you use the following syntax:

object->method(arg1, arg2, …)

• object: The object that has the method you want to work with
• method: The name of the method you want to execute
• arg1, arg2, etc.: The arguments required by the method, if any

Here's an example:

$inv = new Invoice('BONAP', 59.85, .07);

$invoice_total = $inv->calculate_total();

Configuring php.ini for debugging

Your first step in setting up PHP for debugging is the php.ini file, which is the PHP configuration file. In the XAMPP web development environment that I discuss in Book 1, Chapter 2, here are the default locations of php.ini:

• Windows: C:xamppphpphp.ini
• Mac: /Applications/XAMPP/xamppfiles/etc/php.ini

If you can't locate the file, make sure your Apache web server is running, open the XAMPP Dashboard (http://localhost/dashboard), and click PHPInfo. Look for the Loaded Configuration File setting, as shown in Figure 1-7.

Open php.ini in your favorite text editor, then modify the following settings (php.ini is a long document, so you should search for each setting to save time):

• display_errors: Determines whether PHP outputs its error messages to the web browser. In a production environment, you want display_errors set to Off because you don't want site visitors seeing ugly PHP error messages. However, in a development environment, you definitely want display_errors set to On so you can see where your code went wrong:

  display_errors=On

• error_reporting: Specifies which types of errors PHP flags. The constant E_ALL flags all errors, and the constant E_STRICT flags code that doesn't meet recommended PHP standards. You don’t need E_STRICT in a production environment, but it’s useful in a development environment:

  error_reporting=E_ALL | E_STRICT

With display_errors set to On, you'll now see error messages in the browser window. For example, take a look at the following statement:

display_header('notw.png';

Can you spot the error? Yep: the display_header function call is missing its closing parenthesis. Figure 1-8 shows how PHP flags this error. Notice that the message includes not only the error, but also the location of the file and, crucially, the line number of the statement that generated the error.

Accessing the PHP error log

Setting display_errors to On is very useful in your development environment, but the PHP default is to set display_errors to Off in a production environment. This prevents your visitors from seeing error messages, and it also boosts security because you don't want those visitors seeing sensitive information such as the location of your PHP script.

So what happens when PHP generates an error with display_errors set to Off? It depends on the error, but in most cases you either see a blank web page, or a server error message such as 500 - Internal server error. Neither is particularly helpful, but all is not lost because PHP still records the error message to the PHP error log.

That's nice, but where is this error log stored on the server? That depends on the server, but you can find out by running the following script:

<?php

phpinfo();

?>

This displays the PHP configuration data, which includes an error_log setting that tells you where the PHP error log is stored.

In some cases, you see just the name of a file — usually error_log — and that means the server generates the error log in the same directory as the PHP file that caused the error. So, if you store all your PHP scripts in a php subdirectory, your error log will appear in that subdirectory.

Error messages appear in the error log with the oldest messages at the top, so to see the most recent error, you need to scroll to the bottom of the file.

Debugging with echo statements

You can't set up watch expressions on PHP code, but you can do the next best thing by strategically adding echo (or print) statements that output the current value of whatever variable or function result you want to watch.

For example, here's a loop that generates a dozen random numbers between 1 and 100. To watch the random values as they’re generated, I included an echo statement within the loop:

<?php

for ($i = 0; $i < 12; $i++) {

$randoms[$i] = rand(1, 100);

echo $randoms[$i] . '<br>';

}

?>

Alternatively, you could wait until the loop completes and then run print_r($random) to output the entire array.

Another good use of echo statements for debugging is when your PHP code fails, but you don't get an error message. Now you have no idea where the problem lies, so what’s a web developer to do? You can gradually narrow down where the error occurs by adding an echo statement to your code that outputs a message like Made it this far!. If you see that message, then you move the echo statement a little farther down the code, repeating this procedure until you don't see the message, meaning the code failed before getting to the echo statement.

Alternatively, you can sprinkle several echo statements throughout your code. You can either give each one a different output message, or you can take advantage of one of PHP's so-called magic constants: __LINE__. This constant tells you the current line of the code that’s being executed, so you could add the following echo statement throughout your code:

echo 'Made it to line #' . __LINE__;

Debugging with var_dump() statements

PHP features such as echo and print_r make it easy to see values associated with variables and arrays, but sometimes your debugging efforts require a bit more information. For example, you might want to know the data type of a variable. You can get both the data type and the current value of a variable or expression by using PHP's var_dump() function:

var_dump(expression(s));

• expression(s): One or more variable names or expressions

Here's an update to the random number generator that dumps the value of the $randoms array after the loop:

<?php

for ($i = 0; $i < 12; $i++) {

$randoms[$i] = rand(1, 100);

}

var_dump($randoms);

?>

Here’s an example of the output:

array(12) { [0]=> int(44) [1]=> int(92) [2]=> int(61) [3]=> int(61) [4]=> int(12) [5]=> int(60) [6]=> int(14) [7]=> int(46) [8]=> int(73) [9]=> int(29) [10]=> int(8) [11]=> int(71) }