PHP 5.5.17 is available

substr_compare

(PHP 5)

substr_compare Confronto tra due stringhe a partire da una data posizione per n caratteri, sicuro con i dati binari e, opzionalmente, senza distinguere tra lettere maiuscole e minuscole

Descrizione

int substr_compare ( string $main_str , string $str , int $offset [, int $length [, bool $case_insensitivity ]] )

La funzione substr_compare() confronta main_str dalla posizione offset con la stringa str per length caratteri di lunghezza.

Restituisce < 0 se main_str dalla posizione offset è minore di str, > 0 se è maggiore di str, e 0 se sono uguali. Se length è uguale o maggiore della lunghezza di main_str ed è impostato il parametro length, substr_compare() visualizza un warning e restituisce FALSE.

Se case_insensitivity è TRUE, il confronto non distingue tra lettere maiuscole e minuscole.

Example #1 Esempio di uso di substr_compare()

<?php
echo substr_compare("abcde""bc"12); // 0
echo substr_compare("abcde""bcg"12); // 0
echo substr_compare("abcde""BC"12true); // 0
echo substr_compare("abcde""bc"13); // 1
echo substr_compare("abcde""cd"12); // -1
echo substr_compare("abcde""abc"51); // warning
?>

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User Contributed Notes 3 notes

up
5
jimmetry at gmail dot com
1 year ago
When you came to this page, you may have been looking for something a little simpler: A function that can check if a small string exists within a larger string starting at a particular index. Using substr_compare() for this can leave your code messy, because you need to check that your string is long enough (to avoid the warning), manually specify the length of the short string, and like many of the string functions, perform an integer comparison to answer a true/false question.

I put together a simple function to return true if $str exists within $mainStr. If $loc is specified, the $str must begin at that index. If not, the entire $mainStr will be searched.

<?php

function contains_substr($mainStr, $str, $loc = false) {
    if (
$loc === false) return (strpos($mainStr, $str) !== false);
    if (
strlen($mainStr) < strlen($str)) return false;
    if ((
$loc + strlen($str)) > strlen($mainStr)) return false;
    return (
strcmp(substr($mainStr, $loc, strlen($str)), $str) == 0);
}

?>
up
0
Skyborne
2 years ago
Take note of the `length` parameter: "The default value is the largest of the length of the str compared to the length of main_str less the offset."

This is *not* the length of str as you might (I always) expect, so if you leave it out, you'll get unexpected results.  Example:

<?php
$hash
= '$5$lalalalalalalala$crypt.output.here';
var_dump(substr_compare($hash, '$5$', 0)); # int(34)
var_dump(substr_compare($hash, '$5$', 0, 3)); # int(0)
var_dump(PHP_VERSION); # string(6) "5.3.14"
?>
up
-2
sleek
9 years ago
Modified version of the original posted function. Use this one:

<?php
if (!function_exists('substr_compare')) {
    function
substr_compare($main_str, $str, $offset, $length = NULL, $case_insensitivity = false) {
       
$offset = (int) $offset;

       
// Throw a warning because the offset is invalid
       
if ($offset >= strlen($main_str)) {
           
trigger_error('The start position cannot exceed initial string length.', E_USER_WARNING);
            return
false;
        }

       
// We are comparing the first n-characters of each string, so let's use the PHP function to do it
       
if ($offset == 0 && is_int($length) && $case_insensitivity === true) {
            return
strncasecmp($main_str, $str, $length);
        }

       
// Get the substring that we are comparing
       
if (is_int($length)) {
           
$main_substr = substr($main_str, $offset, $length);
           
$str_substr = substr($str, 0, $length);
        } else {
           
$main_substr = substr($main_str, $offset);
           
$str_substr = $str;
        }

       
// Return a case-insensitive comparison of the two strings
       
if ($case_insensitivity === true) {
            return
strcasecmp($main_substr, $str_substr);
        }

       
// Return a case-sensitive comparison of the two strings
       
return strcmp($main_substr, $str_substr);
    }
}
?>
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