w3resource

PHP : addcslashes() function

Description

The addcslashes() function is used to add backslashes in front of the specified characters in a string.
Note : In PHP \0 (NULL), \r (carriage return), \n (newline), \f (form feed), \v (vertical tab) and \t (tab) are predefined escape sequences.

Version:

(PHP 4 and above)

Syntax:

 addcslashes (string_name, charlist)

Parameters:

Name Description Required /
Optional
Type
string_name The string to be escaped.. Required String
charlist Sequence of characters. Optional String

Return values:

The escaped string.

Value Type: String.

Pictorial Presentation:

php-string-addcslashes()

Example:

<?php
echo addcslashes('w3resource.com', '0..9');
echo '<br>';
echo addcslashes('w3resource.com', '.');
echo '<br>';
echo addcslashes('Welcome to w3resource.com','t');
echo '<br>';
echo addcslashes('Welcome to w3resource.com','A..Z');
echo '<br>';
?>

Output:

w\3resource.com
w3resource\.com
Welcome \to w3resource.com
\Welcome   to w3resource.com

View the example in the browser

See also

PHP Function Reference

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PHP: Tips of the Day

PHP - How do I implement a callback in PHP?

The manual uses the terms "callback" and "callable" interchangeably, however, "callback" traditionally refers to a string or array value that acts like a function pointer, referencing a function or class method for future invocation. This has allowed some elements of functional programming since PHP 4. The flavors are:

$cb1 = 'someGlobalFunction';
$cb2 = ['ClassName', 'someStaticMethod'];
$cb3 = [$object, 'somePublicMethod'];

// this syntax is callable since PHP 5.2.3 but a string containing it
// cannot be called directly
$cb2 = 'ClassName::someStaticMethod';
$cb2(); // fatal error

// legacy syntax for PHP 4
$cb3 = array(&$object, 'somePublicMethod');

This is a safe way to use callable values in general:

if (is_callable($cb2)) {
    // Autoloading will be invoked to load the class "ClassName" if it's not
    // yet defined, and PHP will check that the class has a method
    // "someStaticMethod". Note that is_callable() will NOT verify that the
    // method can safely be executed in static context.

    $returnValue = call_user_func($cb2, $arg1, $arg2);
}

Modern PHP versions allow the first three formats above to be invoked directly as $cb(). call_user_func and call_user_func_array support all the above.

Notes/Caveats:

  1. If the function/class is namespaced, the string must contain the fully-qualified name. E.g. ['Vendor\Package\Foo', 'method']
  2. call_user_func does not support passing non-objects by reference, so you can either use call_user_func_array or, in later PHP versions, save the callback to a var and use the direct syntax: $cb();
  3. Objects with an __invoke() method (including anonymous functions) fall under the category "callable" and can be used the same way, but I personally don't associate these with the legacy "callback" term.
  4. The legacy create_function() creates a global function and returns its name. It's a wrapper for eval() and anonymous functions should be used instead.

Ref : https://bit.ly/2Zmqil0