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PHP: substr_compare() function

Description

The substr_compare() function is used to compare two strings from a given starting position in the main string.

Version:

(PHP 5)

Syntax:

substr_compare(main_string, compare_string, star_pos, length, case_insensitivity)

Parameters:

Name Description Required /
Optional
Type
main_string The main string. Required String
compare_string The string to be compared. Required String
star_pos The starting position in the main string. Required Integer
length A positive number : Start at the specified position in the string.
A negative number : Start at a specified position from the end of the string.
Optional Integer
case_insensitivity If set TRUE comparison is case insensitive. Optional Boolean

Return value:

0 : If two main_string=compare_string
<0 : if the length of the main_string from the starting position is less than the compare_string
>0 : if the length of the main_string from the starting position is greater than the compare_string.

Value Type: Integer.

Pictorial Presentation

string_substr_compare

Example:

<?php
echo substr_compare('uvwxyz', 'uv', 1, 2).'<br>';
echo substr_compare('uvwxyz', 'uvw', 1, 2).'<br>';
echo substr_compare('uvwxyz', 'uv', -2, 2).'<br>';
echo substr_compare('uvwxyz', 'xy', 1, 2).'<br>';
echo substr_compare('uvwxyz', 'xyz', -3, 3).'<br>';
?>

Output:

1
1
4
-2
0 

View the example in the browser

See also

PHP Function Reference

Previous: strtr
Next: substr_count



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