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PHP Tutorial - Advanced PHP Topics

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Require

The require() statement includes and evaluates a specific file. The require() and include() statements are similar in every way except how they handle errors. When there is an error the include() statement produces a warning but the require() statement results in a fatal error. The require statement is used when you want a missing file to halt the processing of the page. In this case, if include() is used even then the script will keep on running regardless of the missing file.

Example

<?php

require 'welcome.php';

require $welcomefile;

require ('welcomefile.txt');

Include

The include() statement includes and evaluates a specified file. The include() statement works in the same way as the require() statement. The basic difference between them is that when an error occurs the include() statement gives a warning whereas the require() statement gives a fatal error.

Example

fruit.php

<?php

$color = 'red';

$fruit = 'apple';

test.php

<?php

echo "A $color $fruit"; // A

include 'vars.php';

echo "A $color $fruit"; // A red apple

Variable Functions

There is a concept of variable functions in PHP. The concept of variable function is that if a variable name has parentheses appended to it, then PHP will look for the function with the same name as the variable and will try to execute it. This can be used to implement callbacks and function tables.

Example

<?php

function fun() {

echo "In fun()<br />\n";

}

function abc

($arg = '')

{

echo "In abc(); argument was '$arg'.<br />\n";

}

// This is a wrapper function around echo

function echoit($string)

{

echo $string;

}

$func = 'fun';

$func(); // This calls fun()

$func = 'abc';

$func('test'); // This calls abc()

$func = 'echoit';

$func('test'); // This calls echoit()

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