PHP - strncmp

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Metóda - strncmp

(PHP 4, PHP 5, PHP 7)

The strncmp() function compares two strings up to the given length. The function is `case sensitive and binary safe.

The first two parameters must be strings, otherwise the function can return misleading results.

Procedurálne

• function strncmp (string $str1, string $str2, int $len) : int

Parametre

Názov	Dátový typ	Predvolená hodnota	Popis
$str1	string		The first string for comparing.
$str2	string		The second string for comparing.
$len	int		The number of characters to be compared in both strings.

Mávratovej hodnoty

Vracia: int

Returns 0 if both strings are equal up to the specified length, or if the last parameter is 0. If the first string is greater than the second one, returns a positive number, otherwise returns a negative number.

The result also can be null if one of the first two parameters is an array/object, or false if the last parameter is smaller than 0.

Príklady

Let's try to compare 2 strings at first and notice the difference between lower-case and upper-case letters:

<?php
var_dump(strncmp('hello', 'hello world', 5));       // int(0)
var_dump(strncmp('hello', 'hello world', -1));      // Emits a warning and returns FALSE
var_dump(strncmp('different', 'strings', 0));       // int(0)
var_dump(strncmp('Hello World', 'hello world', 5)); // int(-32)
var_dump(strncmp('world', 'hello world', 5));       // int(15)

var_dump(strncmp('hello world', 'hello world', 11));    // int(0)
var_dump(strncmp('hello world', 'hello world', 27));    // int(0)

We can see that if the length exceeds the length of both strings, the result will be the same.

Now let's try to pass other parameter types than strings:

<?php
var_dump(strncmp(false, 'hello world', 1));     // int(-1)
var_dump(strncmp(false, 'hello world', 11));    // int(-11)
var_dump(strncmp(array('hello', 'world'), 'hello world', 5));   // Emits a warning and returns NULL
var_dump(strncmp(100, 300, 1));                 // int(-2)
var_dump(strncmp(100, 300, 5));                 // int(-2)

We can see the results are very misleading in some cases.