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If you are new to PHP or just need to refresh your skills, this is the place to start. This series of tutorials will give you the basic knowledge you will need to create a simple PHP website.

PHP is a reflective programming language originally designed for producing dynamic web pages.[1] PHP is used mainly in server-side scripting, but can be used from a command line interface or in standalone graphical applications. Textual User Interfaces can also be created using ncurses.

PHP Manual
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Variable functions

PHP supports the concept of variable functions. This means that if a variable name has parentheses appended to it, PHP will look for a function with the same name as whatever the variable evaluates to, and will attempt to execute it. Among other things, this can be used to implement callbacks, function tables, and so forth.

Variable functions won't work with language constructs such as echo(), print(), unset(), isset(), empty(), include(), require() and the like. You need to use your own wrapper function to utilize any of these constructs as variable functions.

Example 17-14. Variable function example

<?php
function foo() {
    echo "In foo()<br />\n";
}

function bar($arg = '')
{
    echo "In bar(); argument was '$arg'.<br />\n";
}

// This is a wrapper function around echo
function echoit($string)
{
    echo $string;
}

$func = 'foo';
$func();        // This calls foo()

$func = 'bar';
$func('test');  // This calls bar()

$func = 'echoit';
$func('test');  // This calls echoit()
?>

You can also call an object's method by using the variable functions feature.

Example 17-15. Variable method example

<?php
class Foo
{
    function Variable()
    {
        $name = 'Bar';
        $this->$name(); // This calls the Bar() method
    }
    
    function Bar()
    {
        echo "This is Bar";
    }
}

$foo = new Foo();
$funcname = "Variable";
$foo->$funcname();  // This calls $foo->Variable()

?>

See also call_user_func(), variable variables and function_exists().

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Another Useful functions:


zend.variables | zend-api.zend-u-delete-global-variable | zend-api.zend-print-variable | zend-api.zend-get-compiled-variable-value | zend-api.zend-get-compiled-variable-name | zend-api.zend-delete-global-variable | security.variables | reserved.variables | migration4.variables | language.variables.variable | language.variables.scope | language.variables.predefined | language.variables | language.variables.external | functions.variable-functions | function.variant-xor | function.variant-sub | function.variant-set | function.variant-set-type | function.variant-round | function.variant-pow | function.variant-or | function.variant-not | function.variant-neg | function.variant-mul | function.variant-mod | function.variant-int | function.variant-imp | function.variant-idiv | function.variant-get-type | function.variant-fix | function.variant-eqv | function.variant-div | function.variant-date-to-timestamp | function.variant-date-from-timestamp | function.variant-cmp | function.variant-cat | function.variant-cast | function.variant-and | function.variant-add | function.variant-abs | function.stats-variance | function.stats-covariance | function.mb-convert-variables | function.import-request-variables | function.define-syslog-variables | class.variant |


PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. If you are new to PHP and want to get some idea of how it works, try the introductory tutorial. After that, check out the online manual, and the example archive sites and some of the other resources available in the links section.