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:
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
Previous: String
Next: addslashes
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:
- If the function/class is namespaced, the string must contain the fully-qualified name. E.g. ['Vendor\Package\Foo', 'method']
- 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();
- 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.
- 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
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