You can get the value of RAND_MAX with the function getrandmax(). Then if you desire a random number larger than that, you have to specify the min and max bounds as parameters, eg rand(0, 100000) will return a random number between 0 and 100000 inclusive - so both 0 and 100000 can be returned.

For example:

<!--?php // random number between 0 and RAND_MAX:
echo rand(); // output: 28688 (for example)
// random number between 37 and 50:
echo rand(37, 50); // output: 44
// find out the value of RAND_MAX:
echo getrandmax(); // output: 32767
// get a larger random number by specifying min and max:
echo rand(0, 1000000); // output: 351990
?>

The output shown in the comments above is as an example. Since it is generating random numbers, the numbers generated are very likely to be be different every time.

In this example, we're going to use the following example 5 line file, saved as file.txt:

line 1
line 2
line 3
line 4
line 5

In the same directory as file.txt, we're going to work with the PHP file test.php. We'll outline the file reading functions below.

readfile()

readfile() is the least useful of the file functions. As a parameter, it takes a string which specifies the location of the file to read - this can be relative or absolute; since our file is the same directory as the script, we just need to pass the string 'file.txt' as this paramter. We call the function using the code readfile('file.txt') and it prints out the contents of the file straight to the browser:

// readfile() writes the contents of the file straight to the browser
echo 'Contents of file.txt using readfile():<br>';
readfile('file.txt');

The disadvantage of readfile() is that it doesn't allow you to manipulate the file contents before displaying it - the next two functions we're going to look at will allow you to do that.

file()

The code file('file.txt') will read the contents of file.txt into an array, which you can then manipulate in your scripts and display yourself. Each line of the file is stored in a seperate element of the array, this means that we can access and manipulate each line of the file seperately using normal array notation.

// file() loads the contents of file.txt into an array, $lines
// each line in the file becomes a seperate element of the array.
$lines = file('file.txt');

// now loop through the array to print the contents of the file
echo 'Contents of file.txt using file():<br>';
foreach ($lines as $line)
{
echo htmlspecialchars($line) . '<br>';
}

// we can also access each line of the file seperately
echo '3rd line of the file: "' . htmlspecialchars($lines[2]) . '"<br>';

In this example, we've loaded the contents of file.txt into an array called $lines then used foreach to loop through the array and display each line on the user's browser. We then use $lines[2] to access the third line of the file (the element at array index 2, since line 1 is $lines[0]).

You may notice that we've used a function called htmlspecialchars() when displaying the file's contents - this enables that special characters used in HTML, such as > and " are displayed correctly. This illustrates the power of file() over readfile() since readfile() was unable to perform this kind of processing.

get_file_contents()

The last method we will look at is get_file_contents('file.txt') which is similar to file() however rather than returning an array, it returns a string with all the lines of the file. We can manipulate and display this in a similar way as with file():

// file_get_contents() reads the file and places the contents in a string
$fileString = file_get_contents('file.txt');
echo 'Contents of file.txt using file_get_contents():<br>';
echo nl2br( htmlspecialchars($fileString) );

Since we have no way of seperating the lines with this method, we've used the nl2br() function which converts line breaks in the string (represented by the special character n) into the HTML line break <br /> so that the file will display correctly on the visitor's browser.

The full contents of test.php is below:

<!--?php<br /--> // file() loads the contents of file.txt into an array, $lines
// each line in the file becomes a seperate element of the array.
$lines = file('file.txt');

// now loop through the array to print the contents of the file
echo 'Contents of file.txt using file():
';
foreach ($lines as $line)
{
echo htmlspecialchars($line) . '&lt;br&gt;';
}

// we can also access each line of the file seperately
echo '3rd line of the file: "' . htmlspecialchars($lines[2]) . '"&lt;br&gt;';
echo '&lt;br&gt;';

// file_get_contents() reads the file and places the contents in a string
$fileString = file_get_contents('file.txt');
echo 'Contents of file.txt using file_get_contents():
';
echo nl2br( htmlspecialchars($fileString) );
echo '&lt;br&gt;';

// readfile() writes the contents of the file straight to the browser
echo 'Contents of file.txt using readfile():&lt;br&gt;';
readfile('file.txt');
?&gt;

The output from test.php is:

Contents of file.txt using file():
line 1
line 2
line 3
line 4
line 5
3rd line of the file: "line 3 "

Contents of file.txt using file_get_contents():
line 1
line 2
line 3
line 4
line 5

Contents of file.txt using readfile():
line 1 line 2 line 3 line 4 line 5

IE we have an array called $fruitBasket which contains 5 strings, each of which is the name of a fruit. We want to find out if there is an Apple in the $fruitBasket - is there an element "Apple" in the array?

We do this with the following code:

<?
// create an array of strings called $fruitBasket:

$fruitBasket = array( "Apple", "Orange", "Mango", "Lemon", "Pear" );
// use the in_array() function to check if "Apple" is in the array:
if( in_array("Apple", $fruitBasket) )
{
  echo "Apple is in the array";
}
else
{
  echo "Apple is not in the array";
}
?>

This code uses the in_array() method to check if the element "Apple" exists in the array $fruitBasket:
in_array("Apple", $fruitBasket)

in_array() takes two parameters here: firstly the object we're looking for, in this case "Apple", and secondly the array which we're looking in, $fruitBasket. It then returns a boolean value: true if "Apple" is in the array, or false if it isn't.

References: php.net manual: in_array() function

What one you should use depends on the situation; require() is best suited for loading files that are essential to the rest of the page - for example if you have a database driven website then using require() to include a file containing the database login and password is clearly preferred over using include(). If you used include() in this situation, then you may end up generating more warnings and errors than you had intended.

include() should be used when it isn't essential for that file to be loaded to execute the page. This is best used in situations where the file isn't essential to the processing of the page (for example a footer file), so if the file isn't present then the user can still view the site. You should, of course, make sure that all files you include() and require() are going to be available.

In PHP versions prior to 4.0.2. there was slightly different behaviour of require(). If you used a require() statement in an if block then the require() statement will always make sure that the file you're require()ing is readable, regardless of whether the condition was true for that if block to be processed. This is best illustrated with the following code example:

<?
$a = 1;

  if($a == 2) {
    require("header.php");
  }
?>

In this example, PHP versions before 4.0.2. will always make sure that header.php is available, but it will only actually execute the contents of it if $a is equal to 2.

From php.net:

Note: Prior to PHP 4.0.2, the following applies: require() will always attempt to read the target file, even if the line it's on never executes. The conditional statement won't affect require(). However, if the line on which the require() occurs is not executed, neither will any of the code in the target file be executed. Similarly, looping structures do not affect the behaviour of require(). Although the code contained in the target file is still subject to the loop, the require() itself happens only once.

To add an extension to be parsed for php, create or edit a file called .htaccess (with the dot first) containing the following line:
AddType application/x-httpd-php .html .moo .htm
This tells the server to check for php code and execute it in files with extensions .html, .moo or .htm. So upload that .htaccess file in the same folder as your .html files with PHP code inside them (using PHP tags: <?php ... ?>) then when you view them in the browser, the PHP should be dealt with as you'd expect from a PHP page.

To calculate the square root of a number, we can also use the sqrt(number) function.

Example

Some example code showing how to calculate roots in PHP is below:

<?php
// Square root
echo sqrt(49) . "<br />";  // square root of 49
echo pow(49,1/2) . "<br />"; // alternative to square root of 49
echo pow(8,1/2). "<br />"; // square root of 8

// cube root
echo pow(8,1/3). "<br />"; // cube root of 8
echo pow(27,1/3). "<br />"; // cube root of 27

// higher roots
echo pow(390625,1/4). "<br />";
echo "25^4 = " . pow(25,4) . "<br />";

echo pow(1234, 1/6). "<br />";
?>

The output from this example is as follows:

7
7
2.8284271247462
2
3
25
25^4 = 390625
3.2750594908837

PHP has a function built in to do this: $x^n =$ pow(x,n).

Examples of 'Power Of'

Here are some examples, which raise a number to the power of another and display the output.  In the examples, <br /> inserts a line break to display the results neatly.

<?php
echo "3^5 = " . pow(3,5) . "<br />"; // 243
echo "2^9 = " . pow(2,9) . "<br />"; // 512
// Anything raised to the power of 0 is 1:
echo "99^0 = " . pow(99,0) . "<br />"; // 1
// Negative powers:
echo "3^-1 = 1/3 = " . pow(3,-1) . "<br />"; // 1/3 = 0.3333
echo "3^-2 = 1/(3^2) = " . pow(3,-2) . "<br />"; // 1/9 = 0.1111
echo "<br />";

// Loop through 2 raised to the 0,1,2,...,10:
for($i=0;$i<=10;$i++)
{
  echo "2^" . $i . " = " . pow(2,$i) . "<br />";
}
?>

Output of the example:

3^5 = 243
2^9 = 512
99^0 = 1
3^-1 = 1/3 = 0.33333333333333
3^-2 = 1/(3^2) = 0.11111111111111

2^0 = 1
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16
2^5 = 32
2^6 = 64
2^7 = 128
2^8 = 256
2^9 = 512
2^10 = 1024

Good luck! If you have any questions about this article then please post a comment!